Love the history - architecture and original finishes (copper elevators!) are awesome. Outdated finishes (old carpet, really small bathrooms, shower water that randomly changes from cold to scalding) are not
.
Location is excellent - walk to anything you want downtown, train stop is a block away, adjacent to Seamus McCaffrey's and Ghost Lounge.
We stayed one night and didn't have any problems with thin walls or cleanliness.
Pool is up on the 3rd floor, which is cool.
Price is really good.
Overall, if you ever want to stay downtown and save some bucks, I totally recommend the Hotel San Carlos.
Hotel San Carlos, if you are reading this, please please modernize the hotel somewhat (see Hotel Valley Ho) and I guarantee you will immediately draw a crowd.