AirBnB

I've used Airbnb and all the other companies in Italy and other countries. Each policy is different--all you can really do is read the fine print. I never book anything if I could not live with if I lost a deposit and could not recover it. Any owner worth their salt will respond to nay questions you have about a place or policy.
I'm one of the many fans of Booking.com, which also offers apartment rentals. You still have to carefully note cancellation dates, etc., but if you are staying in multiple locations, I find it helpful to have them all organized in the same app.

In 2017, we had excellent experiences in Rome and Positano. Read reviews and policies carefully, and look for superhosts.

I have used Air BnB all over Europe, including Rome, and have another reserved in Florence next month.

Regarding cancellation, read each listing's policy carefully. Pay attention to when the free cancellation period ends (may be 48 hours after booking, seven days before checkin, or two days, or 24 hours before). There may be a point close to checkin when you get only part of your stay refunded. That will be spelled out in the listing's cancellation policy.

You do have to pay for all or part of your stay when you book (you can choose which option at checkout). If you cancel w/in the cancellation period, you get it all back. I have cancelled several stays and gotten my refund within a day or two.

If you haven't used Air BnB before I encourage you to read every review for a property you're interested in and read the hosts "house rules" included in the listing.

We've had nothing but positive experiences in Italy with Airbnb. Everyone is right--read and reread the listing for details like cancellation policies. You can search for units using filters (washing machine, balcony, ground floor, heat and a/c, e.g.) which will help you narrow down your options to exactly what you want before you start combing each listing for details. Read the reviews as well.
I think that sometimes you won't see the negative ones as often because people fear being negatively rated as a guest by the host. That can affect future hosts willingness to take you as a tenant. I just look for properties with many reviews instead of just a few. We have had to cancel once and had no problems with getting a refund - you are working with Airbnb, not the host, so that is helpful, I think. I will tell you that my sister had one unfortunate experience in Rome with the apartment not being what it was advertised to be. The owner had had a flood and it was filled with mold when she arrived. He should have informed Airbnb and cancelled her reservation. She had to deal with him at check in, which was pretty ugly I'm told, but Airbnb quickly refunded her deposit in full and she found another place without a problem. Nearly all of our hosts have been helpful, welcoming and very attentive to every detail in their properties. This has been especially true for hosts who make hosting their profession.

We used a subsidiary of AirB&B (Homeaway or something similar) for 4 night stay in Venice in for 5 people in 2018. We found a lovely-looking place but it was a new listing with only one prior guest. Alas, with only a week before our arrival, the host cancelled. We frantically worked with the company and ended up with 2 properties for two nights each. They were beautiful but we would have preferred not to move midway. I agree w/other comments - only stay at properties with multiple positive reviews. Also be aware the definition of "bedroom" may mean "alcove" or "couch." There is definitely a tradeoff - lower costs than a hotel, but more variables and more that can go wrong, consuming your vacation hours to resolve.

We rented a beautiful Air BnB in Rome. After the prior guests had checked out the managers did not make sure that everything in the unit was still in good condition. Two large screen TVs did not work at all ( they blamed it on the building but we could hear TVs from other apts) and the refrigerator also didn’t work. I had gone shopping and lost all that food. It was over the New Year’s holiday and we were told they couldn’t get repairmen to come fix them. I wished we were in a nice hotel not dealing with these problems at a pricey Air BnB rental!

All good points above. A couple additional thoughts:
Convert the currency to euros before you book. It will save you a second conversion fee charged by the booking platform.
Booking.com has a neat combination of apartments/hotels/etc, whereas Air bnb does not offer hotels.

There are also a number of rental agencies in Italy, that are recommended. Just don't use Summer In Italy. They did an unethical switcheroo on us on our second rental with them.
Many properties are listed on several websites - see if you can find the name (usually part of the title of the listing), then google it in quotes to see who is offering the best price. In my experience, Airbnb's fees are getting pricey, and a few times I've found cheaper apartment (with different reviews) on booking or homeaway. Worth checking.
Oh, and air bnb has a method to their listings order, so make sure you exhaust the complete list before settling on one. Some owners pay more to be higher in the search engine, but that doesn't make their place any better.
Have fun exploring!

Just one more thing to look for? Sometimes what is advertised as a bed is a pull-out in a living space, with the expectation that 2 people will share it. In short, 1 actual bedroom that sleeps 2, and 2 on the pullout in the living space. Depending on ages and gender mix of your family, that arrangement may not be optimal.

And yes, pay close attention to things like cleaning and other attached fees. Those can sometimes be high enough to really kick up the price of a short stay. Averaged out over a longer stay, different story.

We have rented AirBNB in Paris, Rome, Florence and had great experiences but that is because I put in the work. We only stay in an apartment for stays of 3+ days, otherwise it is a Hotel. Location is very important to me to close (short walk) to a subway, restaurants, grocery store, walkable to museums etc. So all of that is researched before I even look at properties. The property must be in my desired location, within my budget and have 75+ reviews and I zero in on Superhost properties. Must have an elevator, air conditioning in the summer, washing machine, a separate bedroom (I will do a studio if it meets most of my checklist), blow dryer. I read the last 25-40 or so reviews to see if there is a common complaint (noise that would interrupt sleep, smelly, moldy, dangerous/unsafe etc). I use google translate to read different languages. I also look really closely at pictures. In Paris I failed to see the HUGE lip on the shower, which required my husband to help me step into and out of and was just a daily pain and a fall risk for me.

I’ve used AirB&B before but on our last trip in October, I used booking.com which gave all the accommodation end to end, which worked out very well with very good accommodation for a good price. They all allowed cancellation up to about 2 weeks before our arrival.

I study the pics very carefully. I’m not impressed by pics of art or knick knacks. I want to see if there is a bedside table with lighting, for example, and how the kitchen and bath are laid out. If there are too many personal items in the pics, that might signal that it’s the owners home some of the time. That’s not what I want. My perception is that an owner occupied unit is more susceptible to unexpected cancellations, and might not be as clean. Sometimes there are “clues” that allow you to get to another way to book, like directly through a rental company. I googled the name of one host/company recently and found their direct booking website. The prices were better but they also indicated that smoking was allowed in all units but “ not to worry, spaces are aired thoroughly”. Oh sure, that takes the stench out of pillows, etc! But the Airbnb listings said no smoking allowed. Hmmm. That said, we’ve had great success with rentals on Airbnb and VRBO. Just do your research.

Thank you everyone for the incredibly helpful and detailed advice!

I agree with all posts but the one from igoanywhere was especially good. I would add windows to that list. Sometimes, believe it or not, there might not be any or only one smaller one. Light, light, light!
We look for a couch a well as a chair or two also. Love it when there’s a Nespresso style machine, but not a necessity.

It really resonates about too many personal items. Those that have too many bathroom soaps, shampoos or too much stuff in a kitchen are not even added to our lists. Not to mention clothes hanging up throughout the accommodation!
And, just where is that bed? Loft situations don’t work well for us, so they go by the wayside. Is it crammed into too small a space?
Granted the more details one looks for the more difficult finding a solution, but you really want to be somewhere comfortable.

I've stayed in many Airbnb's from Scandinavia, to United Kingdom and Ireland, to Germany, Spain and France (not yet in Italy). I've had very good experiences. Better, by far, in Europe than in the U.S. I often travel alone so a private room in a home with a host is enjoyable. If anything, Airbnb can be sketchy with location information until after you book. Read any comments about location carefully. Other than that, like any lodging, read reviews for items that are important to you. For me, clean and quiet in a good location is ideal. Whether the TV picks up enough channels or the pool is heated are irrelevant because I won't have time for them anyway.

I was in Italy for three weeks last September and stayed in AirBnBs in every city- Venice, Florence, Siena, Sorrento and Rome. All were excellent!