I'm currently at the St Regis. I've never been a fan of the St Regis "modern vintage chic" look, but if there's anywhere that it might work it would be Moscow, and possibly Dubai.
As a Platinum I was upgraded to what is apparently the largest of the Astor Suites, which is one up from the base full suite. The suite is huge and perhaps the size of the Apartment at the Westin KL which up to now had been the largest Starwood room I'd ever been in.
Service has been very good, with an assigned Butler and a fast-moving concierge. There's a nice pool, jacuzzi, steam room and sauna area that I had completely to myself.
If I had one criticism (beyond not liking the St Regis style in general) it would be the bar programme, which was as weak as I've seen in many other St Regis hotels around the world. I realise many of the best bar teams are tied up to one hotel chain, but I'd strongly recommend the St Regis chain throw a few hundred thousand at the likes of the Dead Rabbit, Happiness Forgets or 28 Hong Kong Street to get some destination bars going. The St Regis Moscow is the only 5* without a bar worthwhile going to - just as is the case in many other cities.