My room was clean, and housekeeping did a great job during my 3-night stay. The decor was modern, with concrete surfaces. Shower pressure was nice.
I did not have any concerns about the overall cleanliness. Staff were helpful, especially since I checked in very early (due to my flight's arrival) and got a room as soon as one became available. I did not try out the breakfast or bring a car, so I cannot comment about those issues. (I ate at the Mason Diner and Pinecrest Diner; both are within a 4-minute walk.)
The hotel lobby did look like it was being renovated. Only one of the two working elevators was working. The working elevator had hard plastic coverings over its interior panels, and there were a few signs indicating upgrades were in progress.
The central Union Square location was a short walk to the Moscone Center. I did not have any overt safety concerns, but unfortunately the surrounding blocks had a lot of scaffolding, making some sidewalks darker than desirable.