Nice Stay in a Nice Hotel
Stayed at the Marriott Union Square for four days in April. My wife had a meeting at the Hyatt around the corner and we stayed at the Marriott for the reward points. The Marriott was not real fancy...It had no restaurant to speak of. But the rooms were clean and functional. The staff was extra friendly and attentive. I made jokes with the bellmen that I was going to sneak out before they could open the door for me. I always lost. 
The location is nice and there are lots of good restaiurants in the area. I walked three blocks to the Top Of The Mark Hopkins for lunch one day, and we liked the steakhouse at the Westin Saint Francis just down the block. We took the double-decker buses and could get anywhere in SFO. One day, we bused to the north end of the Golden Gate and walked all the way back through the Presidio, Marina District, Fort Mason, Fishermen's Wharf, and Lombard Street. If you are not into trying to kill yourself on possibly the most famous city hills in the world, the cable car is just outside the hotel.
Overall, a nice, reasonably priced hotel in a wondeful city.