Great location
If you want to be close to public transit, museums, Chinatown, or retail shopping it's a great location. The staff and general ambience are the Chancellor's other best features. Susan at the concierge desk is extremely helpful, as are all the front desk staff. There's a lot going on at Union Square so it does tend to be noisy, especially nights on the weekends, and there is no air conditioning so you'll want to leave the windows open at least part of the time. There is a ceiling paddle fan though. The beds are pretty comfy, pillows are pretty good. If you pre-purchase the Luques card at a discount, breakfast is a good deal. Pick up a Muni passport at the concierge desk -- you can hop on a cable car at Powell and Post if there's room.