Complete novice with IEMs but I used them for the first time last night. The band was very patient with helping me set up and find a sound I was happy with.
Sounded great and I could hear the vocals and my bass clearly - sometimes I find this gets lost as I stand next to the drums.
I was worried about loosing the live sound experience and feeling disconnected but the opposite happened. Another bonus was I tended to play with less aggressive action which was easier on my fingers.
When starting our 3rd set the sound wasn't right and it took me a few songs to realise I hadn't plugged my headphones back in!!