Just back from a lovely long weekend in Rome, and I wanted to give a plug to the Gran Melia hotel (Villa Agrippina), which seems to get very little positivity on here.
Most of the negativity seems to be around location, which was really not an issue for us. Yes, it is a walk or taxi to most of the sights, but no one hotel can be close to everything. The centre is a very pleasant 15 minute stroll, and Trastavere is only 20 minutes via some lovely views (or 3 minutes by cab).
The hotel itself is lovely - I can imagine the pools in summer are fabulous. The rooms, bar, breakfast and spa were all first class. And off season it is an amazing bargain through Amex FHR with their 3 for 2 offer, particularly if you can upgrade to a 'Red Level' suite, which comes with free drinks and snacks amongst other things.