Just completed a 2 nt stay; thought I'd add my $0.02.

Pros:
*Didn't opt out of the Q3 Promo
*Significantly lower price point than other area HH hotels (~115/nt + can use with the AMEX Sync offer)
*Received upgraded room
*Breakfast buffet wasn't as bad as I would have guessed from other posts (they had lox; I'm a big fan)
*Shuttle to BART / WalMart / Airport was quick; made getting to wherever in the Bay easy

Cons:
*As others have said, the building is older--I can imagine it being really sweet when the cast of Miami Vice rolled up there in '86
*No one seemed to provide consistent info about the shuttle--guy 1 says it runs 24 hrs, every 1/2 hour, plus as requested, guy 2 says it runs 7am-midnight, but only on request, and if requested only on the nearest hour, guy 3 has a different description
*The front desk always appeared overwhelmed; even with only 2 or 3 people waiting to check in, it took 10 or 15 minutes--the phone would ring and the front desk would make those checking in wait until the phone calls were through.
*It was clear outside of the ~3 block bubble the area of town was sketchy at best.

Overall, I'd stay again if the rates were low, and I wasn't staying long / didn't need many amenities from the hotel. I wouldn't be surprised to see it changed to a different brand though--the Hilton name sets expectations higher than what the property is able to deliver.