Italy in 7 1/2 days...Stay in Northern Italy or add in Naples?

You absolutely don't have time to do all this in any sensible way in one week. I would drop Milan and not even consider Naples. With 7 days you barely have time to scratch the surface of Rome and Florence. Two nights is one day. I would do not less than 3 nights in Rome; one day for historic Rome and one for the Vatican and a little more historic Rome on the arrival day. 4 nights in Florence barely scratches the surface of the deep artistic heritage that is this city. I'd do 4 nights one place and 3 the other choosing depending on your interests. The worst part of any trip is the logistics of checking in and out of hotels rushing to and from train stations, traveling etc. By moving so much you devote most of your time to being hassled and frustrated doing the logistics with little time for the experience.

And don't take any advice from someone who hasn't been somewhere in 20 years. Rome is a big city; of course it is 'dirty'. It is also full of fabulous things to see and do. You could easily spend a packed week just there and see amazing things. One day is frankly ludicrous and not worth the trouble.

You have time for 2 (major) cities max, and preferably within ~ 2 hours of each other by train. Rome has grafitti in certain areas (like other European cities) but it's a fabulous and interesting city. I too would disregard the advice in making your decision to spend time there. Whatever shortfalls you may discover will pale in comparison to all the treasures you'll find. Each major city deserves at least 3 full days; more time is required in Rome and other bigger, more spread out cities with a host of blockbuster attractions. I doubt you'll have much time left over but, if you do, then you can take a short side trip or two to a smaller town(s) from the base cities. Also keep in mind that you'll lose some time due to jetlag, so it's not like the 7.5 days will be at 100% fully-functioning, fully-engaged level. You can't arrive in the afternoon and then jump straight to the Vatican Museum (or any other major attraction), for example, and make the most of it after a long flight and lack of adjustment for jet lag. You'll likely need to "ease into" a more busy touring schedule by doing some low-level stuff during your arrival day.

I would pick the two cities based on where you're flying into and out of. Are you flying into and out of Rome, or do you have an open jaw itinerary?

You don't have time to add Naples.
Rome is beautiful and suspect you will not find the people rude or unfriendly. if you yell at them in English and generally act like a rude tourist they might be in return.

I cannot imagine if your friend hated Rome what they would think about Naples.
You would not be able to from Florence easily do a day trip to Rome so changing bases is a good idea for that.

2 days in Rome is really tight, it is large and the main sights take time to see and not super close to each other ; depending on what you want to see of course. If you don't want to go to the Vatican/St. Peter's 2 days is a lot easier than if you do.
I would think you need more time to explore Rome than Florence.

I have to agree with Janet: you are trying to do too much. Which city are you flying into? A couple of years ago we did a trip flying into Venice, where we stayed for 3 nights (my 4th visit to this wonderful, and dirty, city), then trained to Florence and then to Rome. We did a day trip to Pisa from Florence but all together spent about 12 days in Italy, flying back to the US from Rome. I suggest that you pack light and move your base as you go.

As for Rome...I had also visited there for the first time about 20 years ago and did not like it much. I resisted going back but, on this most recent trip, I absolutely loved it. Like any city there are drawbacks...crowded mass transit, dirt, etc., but well worth the time to get to know the people and the sights. The Vatican and St. Peters are amazing and will take a full day.

By the way, we stayed in apartments in Venice and in Florence, a hotel in Rome. In Venice we stayed in a very nice apartment on the Giudecca, which is an island across the canal from the main part of the city. We liked the apartment but we missed being able to walk out the front door and stroll around the heart of the city at night after the cruise ships leave. There were water taxis and water buses but it's not quite the same and we felt a little out of the loop. In Florence our apartment was on the "wrong side" of the river, not far from the Pitti Palace, in a lovely and quiet neighborhood, that really gave us a feel for how the locals live.

Bottom line, in my opinion, schlepp less and enjoy it more!

You might look at the itinerary of Rick's Venice-Florence-Rome tour for an idea of how a well-organized group spends that time, but note that the tour is for one day longer than your plan.

If you choose two cities and want a taste of something else in the mix, then you could, for instance, daytrip from Florence to Siena by bus or plan a half-day stop at Orvieto between Florence and Rome.

P.S. Fall travel dates of the above linked tour are still available.

To my way of thinking, Agnes' advice is spot on! Don't try to do too much in too little time. All you'll have are memories of going from Point A to Point B -- not memories of Italy. Rome, in my opinion, is cleaner than a lot of U.S. cities.

We love Rome; LOVE Rome.

Is there some graffiti? Yes, but so does much of the rest of Europe. The pluses far outweigh any negatives. 'People' are not unfriendly but the locals are not on holiday either so they're busy and don't have time to just chat you up. That's not so different than any other tourist hot spot.

I'd agree that you do not have time for Milan or Naples. At most, you might squeeze in Venice, Florence and Rome but I'd pick two: there's enough in all of them to fill many days. Which two to choose depends on your interests as all three are very different. If you're into Renaissance art, Florence deserves adequate time; if into Roman antiquities, then allow enough days for Rome.

Yes, you would miss out on a lot with only 2 days in Rome. We've spent a total of several weeks there over multiple trips and still feel as if we've just scratched the surface. We had 5 nights in Florence and wish we'd have had more. It's been just long enough since I've last been to Venice but I do know that when we get around to it again, we'll spend more than 2 days.