Am staying at the Excelsior Rome as I type having mulled over the St Regis. One reason for choosing it was the pool area, which I have to say is a real disappointment - small, untidy, water leaking from the air-con in the roof panels, jacuzzi malfunctioning (cold) and generally sub standard. The hotel itself is beautiful though and no complaints there. Surrounding area is very expensive for what it offers, food-wise.
Think I'll shift to the St Regis for the next trip.