I played my first gig with IEM's last night. Total convert.
It was odd for about 5 minutes, then my life changed! I could hear everything everyone else was playing and singing with clarity (except the drummer whom is not mic'd, but I remedied that by quickly throwing a spare mic under his kick and plugged it into my Rolls unit).
I can honestly say I played my best gig ever - I was note perfect, well almost I could hear every detail of my playing, just like when practicing at home - it was an absolute bloody revelation
We were at close quarters with a very noisy, up-for-it, dancing crowd, so for our last number (hands in the air, crowd singing, etc), I pulled my IEM's out of my ears, bloody hell it was loud! And I couldn't hear my bass. Straight back in.
We normally use Yammy powered wedges (the rest of the guys still do), but trying in-ears really has made a helluva difference.
For those interested, its a wired setup: Westone UM1's, a Rolls PM351, with a mix from desk, another line from my amp and a Shure SM58 thrown under the drum kit!