Until my final morning, I would have given the Donatello five stars in every regard, hands down. That changed.
The problem I encountered was at check-out. They have a 10am check-out time, which is a little early, but definitely not ridiculous. However, many might expect it to be the more standard 11am, as I did. I would suggest they explicitly let guests know, verbally, about the check-out time upon check-in.
I did realize early that morning that check-out was 10am. I packed, made a pretty quick trip to their fitness center, and returned to my room no later than 9:50, just enough time to take a quick shower and zip my suitcase. I was already locked out of my room at 9:50: my key card no longer worked. So I had to go down to the lobby, where I was met by attitude and noticeably curt behavior from a previously friendly desk attendant. She had to make a a new room key. I made it back to my room by 9:58, trying my best to hurry. (Of course, it still was before check-out time). At 10:02, housekeeping knocked on my door to get in, even though I had the "do not disturb" marker on the door.
In the end I checked out by 10:15. A 15 minute grace period doesn't seem unreasonable. Of course, I would have checked out just on time had I not been locked out of my room.
It was a stressful process and I must say left a bad taste in my mouth. Despire it being a really good stay until then, it was enough to make me not wish to stay there on my next trip to San Francisco.