Tiny room with poor ergonomics
I was rather disappointed with the Serrano. However, since I hate to complain, I'll mention the positive points first. The location is very good, only a couple of blocks from Union Square and a 5 minute walk to the nearest tram/light rail stop. The reception staff are professional and helpful. The lobby is attractive, and features free tea/coffee and free wine for one hour each evening. If you join the hotel's rewards programme, you get free easy-to-connect wifi throughout the hotel. We also got complementary continental breakfast vouchers, valid at the adjoining restaurant - and the food was pretty good.
However, my room was tiny, barely larger than the queen-sized bed. There was no desk, which is a serious omission for your average business traveller, and very little floor space to spread luggage around. My colleague, who paid the same rate, did get a desk and more space - so presumably you can demand something bigger if you don't mind making a fuss.
Another annoying feature was the glowing light switches. Presumably they are lit to help you find them in the dark, but in my opinion they are far too bright. Given the tiny dimensions of the room, it was like being surrounded by a row of candles all night.
Another couple of things: the television was at the side of the bed, making it difficult to view from the bed; and there was a surprisingly large gap between the toilet and the toilet roll dispenser (fortunately I'm quite tall!). Probably both a result of the inconvenient room size, and whilst neither of these made me seriously grumpy, they're not features I expect to find in a quality hotel.