We choose Siam Society because we were on our way back from Chiang Mai and just in Bangkok for one night before heading out to the islands. Siam Society is not really near a lot of walking district type stuff, but it was only 20 minutes from Suvarnabhumi, and there are a lot of food vendors on their street, which is awesome.
Our room was kind of old-ish, a little shabby but clean. It had a weird little not-a/c front room converted from a driveway where people could smoke, and a giant bathtub that fit two very comfy. It took ages to fill, but it was worth it for a good long traveler soak. They have theme rooms, too, which we glimpsed walking by, but we didn't get one of those (sadly).
Free wifi worked well, there were plenty of plugs to charge stuff, and the room was big. There was no TP in the toilet area, but there was a maid cart nearby another room, so we swiped a roll and were fine. The only really bad thing was that sometime during the night the electricity went out, apparently a fuse, but since the front desk folks didn't speak much English and we don't speak much Thai, it took us a little bit to communicate what was wrong. Once we did, it was back on quickly. But we woke up to a pretty hot room until then.