A big disappointment for the price
My husband and I stayed for 4 nights at this hotel in mid September when we visited San Francisco for his birthday. We chose this hotel largely based on the trip advisor reviews and also based on the location. While the location was certainly fine, I found the hotel itself to be below my usual standard. To this point, I even wanted to check out after the first day/night and move to one of the other nearby hotels like the Westin or Marriott but my husband convinced me it wasn't worth the hassle.
So, the hotel is very tiny. That in itself is not a problem as we have stayed in hotels that are old and small before-particularly in Europe. The issue was that the room really showed it's age. There were marks all over the wall, the furniture was very worn, carpet thin, and it looks way nicer online than it does in person. At the desk there were two outlets one for the lamp and one extra which would be perfect to plug our laptop charger into and set up the laptop on the desk. However the free outlet didn't work. The coffee table looked like a cheap tray spray painted that was raised off the ground. 
The bathroom is split into two parts-an open area with the vanity and then a bathtub/shower and toilet in a tiny room with the door. The vanity looked nice and was updated, too bad it was never cleaned while we were there (see below). The shower was a bit of a joke. Neither my husband or I are particularly tall, 5'5" and 5'8", I was able to just fit under the shower head and he actually wasn't able to! It was so short he had to duck and lean back when he wanted to put his head under the water. The shower head was fixed to the wall as well so there wasn't the option of lifting it off and holding it to the right height. For $400 a night, that was not justifiable.
We also had problems a few times with the cleaners and heard others across the hall from us have issues as well. We had to call and ask housekeeping to make up our room twice before they finally showed up on our first full day there. Our room was finally "cleaned" around 5pm. All she really did was come in and make up the bed, add a couple new towels, empty the garbage and throw a couple new bottles of mini shampoo/conditioner on the vanity. It probably took 5 to 10 minutes. No vacuuming, wiping down any surface in the room, and she did not even wipe down or clean the vanity. There really is no "turndown" service at night either despite what is advertised. It is basically an older man who is like a porter that shows up and puts a bottle of water or two on the desk and two tiny chocolates. That's it. No actual turndown of the bed or room or anything else being done. 
The breakfast offered daily was fine. It was nice to have the option of going down and picking up a few items to bring back to our room. Don't count on eating out in the breakfast area as there is one small table with 3 to 4 chairs and that is all. Also it was nice that there is coffee and a kettle available there during the day too, but this day in age, it would be preferable to have tea/coffee making facilities in our actual room. There was no water in the breakfast room so if the kettle didn't have water you'd have to take it back to your room to add water and then back to the breakfast room to actually make the tea.
The bed was fairly comfortable, though the room wasn't very large and certainly not what I expected for a Junior Suite. Little things like there being no listing of tv channels, no information on nearby amenities or restaurants were a disappointment as well. There was free Wifi which is great but we got kicked out of it constantly when in our room and at some times were not able to connect at all. We did find there to be a tiny room with a computer on one floor for guest use which we used to print out our boarding passes so that was a bonus. At the end when we checked out the person at the front desk could not get the printer working to print us a copy of our receipt. Not a big deal, she said she would email it instead. We did get an email with an attachment which we could not open on our laptop. I emailed back and asked if she could please re-send it in a word document or just put it into the body of the email. I never heard back from her...so I've never actually gotten the receipt even though it's been 3 weeks since we checked out.
The location is fine but I would really recommend looking at other hotels in that area if you want to stay near Union Square. Trust me, upon being there, there were no shortages of other options of both chains or independent hotels within a few blocks.