I waited too long to get one. Now, I wouldn't want to track without it. Seems built well and has been problem free so far. Oddly... it *does* require a battery. But it's not only useful for punching in and out, but is also good for rewinding and playing as you "practice" a part. This also helps in keeping what would otherwise be high mileage and wear and tear on the most used buttons (play and rewind for me). And, of course, you can assign the button functions from the "Preferences" menu on the DP.
Get it. Well worth it.