I have one of these now, but I have 'only' been using it for several hours. (It takes time for the content to collect). It does use "commercial advance (tm)" technology, but i would bet it has been elaborated in some way to accept the additional info that a DVR device can gather (like Rob said).

I would estimate it better than 90% accurate. In 6 hours of watching it made 2 mistakes (missed one commercial and advanced 15 sec in the middle of show). When the commercial skips you actually see about one second of it - just long enough to realize what its doing. In my estimation its accurate enough that I wouldn’t consider turning it off - which can be done easily form the remote or set by show (like xfiles).