We stayed at the Driskill during the first weekend of the recent Austin City Limits festival. It was fun, campy, Texan... and added to the overall ambiance of our trip.
We stayed in a corner room. As noted, the rooms are small, the fixtures are old, but this is part of the charm of the Driskill. The corner room was sunny, but the windows did not open. This led to the room being stuffy, and frankly almost moldy. My allergies (which are usually kept in check, flared up.)
Upsides include the true Texan cowboy decor, the cafe, the central location.
Downsides include the slow elevator, the small and somewhat stuffy room.