Wonderful city to explore with the possibility for use a 'hub' to do day trips to places like cinca terra and pompeii. Basically a must see in Italy. It did have the highest city tax of the places I stayed at in Italy, with a charge of 3.50 Euro per night (this is not included in accomodation costs!). Only takes 1 hour to walk from one side of the city centre to the other although it's not flat terrain in most cases.
Insider Tip:If you're going to the Vatican museum PREORDER YOUR TICKETS ONLINE so you can 'skip the line' (The 2 1/2 hour wait is not worth it). Not an issue at the Colosseum (just get your ticket at the roman forum first - only 10 minute line)
Easy enough to walk everywhere though affordable metro (1.50 Euro)
Meals can be expensive particularly being that menus are structured in a 'starter, first course, second course, side dishes etc. manner with no overlap (ie.ordering a steak is ONLY a steak) preresearch is usef