I just used in-ear monitors for the first time at last night's worship practice. They totally ROCK! I have been using the normal wedge-type monitor, and it works fine. But wow - the in-ear monitor is amazing! I could hear everything extremely clear - bass, guitar, etc.
That level of hearing also helped me lock onto the bass and the guitar much better than I have been able to do in the past. And I could hear other instruments better... I even heard myself better (cause the sound dude added a little drums to my mix, so I could hear my cymbals better).
It just completely rocks.