so, how is driving in Rome

It's not any worse than Florence or the cities you mentioned. Just watch out for the ZTL and the bus only lanes. They have a lot of that in Rome too (not so much in NYC).

Better question is "Why"? What will it accomplish for you to bring yet another vehicle into a crowded city with a very likely chance you'll be fined for driving in a ZTL? Will it bring your pleasure? If you want to see Rome then the easiest way is to hop on the train from Florence city center and be deposited into Rome city center.

Why? Because I have been in Italy for the last six weeks and have a leased car. Use it or lose it. Driving to Venice this week, cheaper than a train, and just about as fast time wise.

Go ahead Jim. Since you have a leased car you might as well use it. Besides with a car you have the flexibility to take some side trips along the way and make stops in some nice places between Florence and Rome, if you are not in a hurry. Don't worry about driving in Rome. Not all of Rome's city center is in the ZTL. Just find accommodations with parking arrangements of some sort, preferably not too expensive.
If you drive to Venice you won't have much use for the car. Parking in Mestre near the station is a bit cheaper than at piazzale Roma. Actually there are also free commuter parking lots at the edges of Mestre from which you can take the bus to the Mestre station. The from Mestre it's just 10 min train ride to Venezia SL

In my opinion, it's not the driving in Rome that's such a hassle, it's the not-driving, i.e., the parking that can make you crazy. If you have that part figured out, it might make sense, in your circumstances, to drive. For example, a number of years ago, my brother was living in Rome. We took a few days from our time in Umbria to visit him. The only parking we could find close to his apartment, where we could leave the car overnight, was metered. We had to remember to get out early in the morning to feed the meter. I can only imagine that it's more congested and that such spots are harder to find now.

si, I booked a hotel in Mestre outside the train station. Easy in/out to Venice. I'm not worried aut driving in Rome at all as long as I know where I'm staying. Roberto, I have probably put 2000 miles in Tuscany alone. I have been everywhere in this region.

I learned to drive in New York City - Brooklyn.

I frequently drive in London, but avoid south of the River.

I have driven in Rome and Naples (and of course, Paris).

New York driving is chump change to driving in Rome. Florence and Toscana are walks in the park.

New York cabbies are well behaved and predictable.

Driving in Rome is - for me - nuts. Mainly because of the motorinos.

And the full and complete lack of parking. Anywhere. Unless you want to pay through the nose to park underground. Been there, done it, got the T-Shirt.

I am (was?) a very confident driver, but I WILL NOT drive in Roma any longer. I will drive OUT of town, but not within. As Nigel mentions, it is a world-class PITA. The motorini alone will give you heart failure. (Well they give ME palpitations.)

I suggest you drive to Roma and find a place with parking for lodging,l probably Prati or Parioli will have some options where parking will cost only and arm and not the proverbial arm-and-a-leg. Take public transportation to go to the sites. Tram, bus, Metro and taxis are IMO very good. (Not as good as Paris, but good.)

Just got back from a month in Italy. While I did not drive myself this trip, I doubt I would have any issues driving anywhere there - except Rome!

The lane markers and other traffic signs just seem to be suggestions rather than rules. The parking is simply insane with every spare millimeter of curb and median space occupied and in many cases double parked on top of it. The expected convention on how to enter round a bouts are completely alien to me (and I have driven in many other European cities with no issues). The cab ride to the Rome airport was more like a NASCAR event than a normal drive with vehicles, including a large UPS truck, zig zagging between the other vehicles and coming within touching distance.

Good luck!

I booked a hotel close to the Vatican that has free parking and shuttle bus service to Rome Centro and the Vatican. Easy drive to location. I'm good.