I am currently staying at the Hyatt Regency SF. I like it because it is close to the office. You will be neither dazzled nor disappointed. The rooms are standard-issue Hyatt. Rooms on the RC level do not have a coffee maker but the other rooms do (go figure). The RC features no amenties anymore. No morning coffee, no afternoon snacks, nothing except keyed access, a phone in the bathroom, and nicer elevator doors. Big deal. The lobby bar is okay. Make sure you tell them to shake the heck out of your martini or it will arrive only sightly chilled (why a bartender whose job depends on tips would be so lazy as to make a bad martini is beyond me). I much prefer the lobby bar at the Park Hyatt and sometimes go there for a drink even if I am at the HR. (The Hyatt website has an internet rate at the PH of $125 on Fri-Sat-Sun so I move there for the weekends and back to the HR on Monday).
I prefer the Hyatt Regency to the GH Union Square which is always overrun with noisy, sloppily-dressed tourists or the Wharf Hyatt which has not only the tourists, but tiny rooms with no views. Oh, one last thing: when checking into the Hyatt Regency, if you can't get a balcony view, ask for a view facing Market instead of Drumm. I think the view is nicer and you aren't bothered by the doorman's whistle at 6 am.