Convenient location, not as many amenities as the Marriott
Stayed here (as a solo traveller) for two nights for a conference. Location is excellent - within walking distance to many restaurants, shopping and coffee. Moscone conference center was just a few minutes walk away.
Check in was quick - was giving a Starwood Preferred Guest room - it had a small table near the entrace as a sitting area. Room was clean, and had floor-to-ceiling windows. No issues with the bathroom. Tons of space for a solo traveller or a couple. The king sized bed was great as is the case with all Westins.
I ended up using the Lobby Wifi. There are a few sitting areas in the lobby area where Wifi could be accessed. One is a lounge area, near the hotel restaurant. You don't have to order to sit there, but you can if you want. There is a TV in this area, and seats are comfortable although the area is dark (lounge-like). Just off the elevator area there are a set of rooms with seats that reminded me of a hospital waiting room. But if you're just checking email, it's not a big issue. 
My only beef with the free Wifi was that when using it on my phone, if it went beyond a few minutes the Wifi would disconnect. This led to me ended up using my 3G connection and will no doubt get a few roaming charges. But what can you expect for free wifi.
My only beef with the hotel is that there didn't seem to be as much in-hotel amenities as the nearby Marriott, which had its own Starbucks and lots of nicer seating areas within. But with many nearby eating and coffee options outside the hotel, it wasn't a big deal.