Just returned from a 5 night stay at the St. Regis. i have stayed at only one other St. REgis (Beijing) and have some experience with other luxury hotels such as FS,RC, and the Oberoi chain.
Room: very modern; reminded me more of a room that should be in the W. It was quite nice but I guess I am used to more traditional luxury. We had one of the lower category rooms. 42" plasma (but no HD feed), large walk in shower (rainfall) and nice soaking tub which opened up to the room. Lines were quite nice and crisp and the king size bed was comfortable. We never ordered room service but the menu look quite nice. My shoes never got shined (and they needed it). It's one of my tests of service-> FS usually picks up on them when I leave them out and shines them. Nonetheless twice daily service, nice toiletries (forget the brand) did help. HSIA was not included (as it never seems to be), which I find rediculous for a hotel that charges $550 a night. it was $14.95. I stayed at a Hilton Garden Inn recently near an airport that was $89/night and they were able to provide free HSIA
Service: Check-in quick. No recognition of status (just a gold) or the fact that I had written in comments that it was our anniversary. Stayed at the Grand in Firenze last year (a luxury collection hotel) and they wished us a happy anniverseary and sent us a bottle of Prosecco. Conceirge recommend a great pizza place (hey we love pizza). I worked out each day and it didnt seem that there was an attendant in the exercise room (but all machines had water and clean towels so maybe they just hid). The service just didnt seem to be on the same level of the FS- the doormen seemed a litle slower in getting the doors open.
Pool/Exercise room: pool quite nice, indoors. no hot tub though. Exercise room was nice- new machines, TVs at all, plenty of cold water available
Location: super close to the Moscone convention center; walking distance to union Square. Kind of dead at night but not huge. Not very close to a lot of the touristy stuff it seemed.
Verdict: it was nice though I probably wouldnt stay there again. i would try either the MO or the FS (i am not a huge RC fan but the ones I have stayed in have been their lesser properties-> Atlanta, Atlanta, Atlanta)