OK stay
My husband, sixteen year old daughter and I have just returned from a 4-day stay at the W in San Francisco. My first overall impression was that the decor was somewhat "dated". These days "hip" is bright, sleek and cool with lots of clean lines, and light stone floors/walls. Instead the decor at the W was dark and more 1990's black with hits of primary colours. Certainly not what I expected for a trendy hotel, but certainly not a deal breaker either. Decor aside, the check-in was fast and efficient.
The decor of the rooms was much nicer and brighter. However, I was disappointed by the size of the beds. I have stayed at other Westins in the past and have always looked forward to their "heavenly" beds. This time the bed, which felt a tad smaller than a double, was far too small for two adults and my husband and I both woke up with knots in our backs. As well, the walls between the rooms were quite thin as I could hear the conversations of my neighbours as well as their music quite clearly. Fortunately, they went to bed around 1 am so I did not complain to the front desk. 
The fitness room is quite well equipped and the pool is a nice size.
Overall, our stay was adequate but I would try a different hotel in future.