Buddy of mine turned me on to these a couple weeks ago, and I waited for the right chance to pounce.
I semi remember when the Line 6 Backtrack came out and I think I glossed over it because I assumed it was just a standard sound recorder and for the price ($100+), I'd have rather gotten something with XLR inputs, mic, etc.
HOWEVER, I didn't realize how this thing works. The main draw is that you basically plug into it, hit the power button and jam. It only starts recording when it hears you playing and it automatically stops and renders a WAV file when you stop playing for 2 secs. Then it starts a new file as soon as you start playing again. If you play something you especially like, you push the 'mark' button and it moves that file into a different folder.
Its fantastic for noodling and sifting through your ideas without a lot of dead air. I think these had ~8 hours on a charge new, mines only getting about 1 hour now so it probably could use a new battery. As far as getting your files off, it connects via USB and appears like a flash drive.
I think it's a cool tool at any reasonable price but I especially decided to jump on it since this was $25.