Stayed at the Hyatt while attending a conference.
Good news: The hotel is clean, housekeeping got it right every time, reservations weren't screwed up. The location is very convenient to the Convention Center, the Gaslamp district, the Midway aircraft carrier museum, and the Marriott. There is a safe but no refrigerator. A supermarket (Ralph's) is within walking distance.
Bad news: Food provided by catering was nothing special, though maybe the cheap stuff was ordered. The bar at the top of the hotel is disappointing. The windows aren't big and are designed to prevent you from looking out while sitting in the low chairs that are near the windows. The train whistle is relentless, though the HVAC unit's fan can be put on high, masking much of the noise.
This is an above average conference hotel but if your conference uses the US Grant hotel for overflow, let them put you there. The location is better for your time off and that hotel is rated higher by this web site.
Maybe it's my age, but it was just weird seeing how many Japanese tourists were smiling and taking pictures of each other in front of the Midway on December 7 (Pearl Harbor anniversary). I'm glad that times have changed.