I use it for artists' markets. I LOVE it! It can be a little tricky to swipe - you have to do it really fast, and sometimes make several attempts, but other than that I've had no issues.
When it arrives, make sure you use your own card at home to trial a sale with the reader so you don't end up stuck with a faulty reader (this happened to a girlfriend of mine - she sent it back and they quickly replaced it), and so you kind of get the hang of it.
My last show, it definitely got me more business since people either didn't bring cash, or ran out by the time they got to me. Out of 5 stars, I'd give it 4.5 (only because it can be tricky to swipe.)
Also, they'll send you a little sign that you can display prominently that lets browser's know you accept cards.