we only stayed for 2 nights before heading to positano and capri but the hotel was perfect!
the room was super clean and the air conditioning (badly needed as it was so hot!) was the BEST! the room was palatial and very elegant. very quiet also. helpful concierge staff. good location!

We stayed 7 nights at St Regis in mid May. Everyone will have different opinions on their stay - our visit was great. I read every review on Travelocity before we booked the St Regis and it did not disappoint. Some things to note:

It is pricey - something you cannot get around.

I loved the bed. I have a hard time sleeping virtually anywhere, including my own home. The bed was so comfortable I was able to sleep like a rock.

Our room was on the 4th floor, overlooking the Piazza Republica. Maybe because we were higher up we did not hear the traffic that others state was loud. When we closed the window - silence.

The bathroom was clean and large enough for me. European hotels can have tiny bathrooms. This one is fine.

Based on comments on this site we never ate in the hotel. Everyone says it is too expensive so we did not even try it. We did drink at the bar late at night - they even stayed open to serve us when we arrived after closing time.

We are in our mid 30's and walked to nearly every site - the exclusion being Vatican city. We took the Metro for 1e.

We found he best food at Monte Caruso (within walking distance). It was always filled with locals. No tourists. Every dish was unique and home made.

The hotel hallways were quite large - not a factor in staying there I suppose.

The concierge hooked us up with a travel agency across the st. for a day trip out of town. Reasonably priced but just an OK guide.

The metro is convienent. At no time, including at 2am, did we feel unsafe walking anywhere in Rome.

After doing some extensive research on my vacation to Rome, I finally decided to go to the St. Regis Grand. I got a pretty good rate at 320 Euros (corporate rate), expecting it to be star quality when I arrive. Truth is, I was not, really. Okay, there should be guest reporting some fine services and awesome rooms. (there were good rooms and not so good rooms mind you). I stayed at what I thoguht was not such a good room. okay, I'm going into some detail here...first off: the lights were too white and bright -- for the halls and the rooms. I heard there was some renovation, but, I'm sure for the normal rate, they could afford to install flat screens in the rooms (and maybe even the bathrooms). It may not help by a mile, but it sure does impress; and satisfy. Next off, the carpet. Old-ish, weak design, dusty. The room I stayed in (202), was not such a good room, but I'm sure there are quite a few like mine. (I simply cannot wonder how they make the rooms looks so good and nice...hmm...). Anyways, I'm sure there are bettter rooms, but some detail must not be overlooked at hand. The bathrooms, on the other hand, were good. period. Good bath products (interesting orange scent) and a pretty deep soaking tub (if not long enough), and beautiful large gold framed mirors adjourn the walls. One complaint though, when showering, the water turns cold then hot or vice versa, even if you fix it at a specific temp.; this happens quite a lot.
Service at the St. Regis was not too bad, for Italy (dont compare it with top hotels in Paris though). They seem helpful at times, and the restaurants they recommend us to were not entirely the best (some good ones albeit), and I did rely on the Michelin guide for the best in Rome. However, unless you're not a gastronomic gourmet, those recommendations are not that bad; sometimes pretty good.
Because of the taxi strike in Rome, I had to walk to the restaurants nearby. It happend 2 days after my trip, and luckily i tasted some of Rome's supposed best before then. The nearby recommendations were not bad though. If there is a taxi strike for some reason, you should avoid limousine service (very pricey) unless you can afford it; but still, I found it to be slightly over the reasonable limit.
The location of the St. Regis is okay; its a long walk to the Spanish Steps and the tourist places, as well as major shops (about 20-30 mins walk to the Steps); the concierge kept assuring me it was only a 10 min walk, -.- . However, on the bright side, there is metro and bus station very nearby, and the train takes 2 stops to the Steps. (beware of pickpockets)
Woud I recommend this hotel? Yes and No:

Yes if:
you're rich. more than willing to pay. can spend. did not really need to save up for this.
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you're staying at a very good room. To be safe, the best suites with the best view
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you don't expect top class perfection for service
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you got a really good rate for a room (maybe corporate rates dont reserve the best sometimes)


No if:
you agree with my fickle criticisms mentioned earlier
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you saved up to pay for the normal rate (even the corporate rates pretty expensive; not even worth what i paied for)
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you're pretty stingy with hotels and you want the best for money
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you stayed at other better hotels (except St Regis is the only one)
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you think the 5 star hotels in Rome are on par with hte 5 star hotels in Paris (incl. what you paid for)

We just returned from two weeks in Italy and ended in Cap Ferrat. The Grand Hotel was impeccable. We are accustomed to staying at Four Seasons level hotels and this hotel was impressive. The imperial romms are very large large and have Murano Glass chandeliers. Every detail was addressed. The staff attended to every detail perfectly. Their head concierge is probably one of the finest in the industry. The lobby lounge is as elegant as the Loius xv restaruant in Monte Carlo. We are very selective in our hotel choices and this one fulfilled just what we were looking for. The best dining choice for view and food in the city was Mirabelle. The view was spectacular.