I always find the http://www.flyertalk.com/forum/starw...read-list.html which is stickied to be a very helpful starting point when researching Starwood hotel opinions on FT. In there you will find the relevent master property threads for many hotels, with London well represented.

As for London recommendations, personally I prefer The Sheraton Park Tower and Le Meridien Piccadilly. Both are genuinely good hotels of a consistenly high quality. Le Meridien has a lounge and is in an excellent location. The Park Tower is close to Harrods and Knightsbridge and some very nice, upscale shopping etc.

The hotels to avoid in my opinion are firstly the W, with poorly planned bedrooms and some noise issues depending on the room you get. It is also very highly priced, so unlikely to offer value. The other one to potentially avoid is the Sheraton Park Lane which is an old hotel and as such has some very poor rooms. That said, it is the cheapest central London option on points, so does offer good value on cash and points in particular, so shouldn't be completely dismissed.

It all depends though on what the OP would be looking for in a hotel, the price they are wanting to pay etc.