Recently stayed here. My first stay in a W. Was quite impressed, was upgraded to a Studio Suite which was very comfortable. Had a pleasant greeting on checkin and the guy delivering my bags was leaving the room before we got there!
We got breakfast and 500 points. Breakfast was of a pretty good standard and I liked the ambiance. Plenty of rotation each day which made going to breakfast more interesting.
We had a room facing the BTS and could hear the trains but we didn't find it disturbing (after spending a year in a third floor apartment fronting a major highway we have been conditioned to noise).
The only thing in terms of Plat recognition which was lacking was the provision of 2 drink vouchers. Although my wife and I aren't big drinkers this is always something we look forward to when staying at PA, LM, Westin or SGS (even the one stay at ROS). Not a deal breaker but the 50% off card we were given didn't get any use.
Overall its not my preferred location but I found it to be pretty good. I booked on points then applied my requalification discount. If I were paying cash Im not sure I would find it good value. I would stay there again if it had a competitive pricing against the other BKK options but in saying that I would stay at any of the SPG hotels there except ROS which I found to be too out of the way for my liking.