Very nice, but noisy at times
I booked the Hilton Bayfront to be as close as possible to the convention center, since I was there for a conference. The hotel is indeed within a few minutes walking distance to the conference center, which is very convenient. The walk to the Gaslamp quarter takes 10-15min, which is fine if your main purpose if the conference anyway.
The check-in was swift and the staff friendly. Checking-out, however, took me almost 20min, because only one out of four or five counters was staffed, which was simply not enough to cope with the rush of people wanting to check out at 9:30am.
My room on the 25th floor was spacious, very clean and well equipped. In particular the work-desk and the high-end office chair were perfect for getting some work done after-hours. The internet access in this hotel was unfortunately not complimentary; instead one has to pay a minimum of $13.95 per day. There is complimentery WiFi access in the lobby of the hotel, but this does not get mentioned anywhere.
The bed and the pillows were fine for me, i.e., I slept well despite having to cope with a 9h time difference. Having said that, I got woken up one night by clanking noises. As it turned out a Dole banana freighter had just arrived and they had started unloading the banana containers onto trucks straight away. Once they had unloaded the ship, they loaded it with empty containers, which turned out to be even noisier. The entire process continued for the next three days & nights, which was a bit annoying, but I suppose there is nothing the hotel can do about it. 
Still, I enjoyed staying at this hotel very much and would recommend it. It might just be better to get a room towards the convention center and not out the back of the hotel overlooking the Dole truck depot.