I got mine about a month and a half ago and I've been using it every week since. It's made my job on the field much easier, since I don't worry about jams anymore. It's completely worth the cash, because it will save you money on batteries and broken paint in the long run.
The only problem I've had with one was when I was using a friend's DM9 and didn't attach my joy rotor properly and it fell off
.. didn't put it down far enough into the feedneck (it was my first time using a DM
). I got it back on and made a run through but then it kept jamming and I got pinched. Although the rotor tends to never have any problems, just make sure you attach it ok!!