Anybody here using IN-EAR MONITORING systems?

If so, what are you using, and are you happy with it?

To me, it looks like a fairly pricey solution, but it does have its advantages:

1) each person can make themselves louder in the mix so you don't get volume wars when people turn up in order to hear themselves

2) if you're using backing tracks in the context of a full band, the in-ear monitors are supposedly the best way to keep people from getting out of synch with the trax