Tony I started using in-ear monitors in about 2013 (when I was playing bass and singing backup in a band) and these are my thoughts on them.
1. If you are going to get some buy high quality, multi-driver IEM's to make them worth while. The cheap ones really don't work much better than ear buds and the good ones are several hundred dollars to start.
2. to work properly they have to seal in your ears, any bleed of ambient sound will mean you'll need to boost the volume which is counter productive to protect from hearing loss
3. when you do get a pair with a good seal you become isolated and can't hear conversations unless someone is speaking into a microphone. My unit (it is an audio technica) has a jack for an ambient mic with a volume control so I can hear what is going on around me between songs. But that mic was 2/3 the cost of the whole unit. I had to get an ambient mic because the fit in my ears was tight to seal them and every time someone talked to me I had to pull one of the monitors out of my ear and after about two sets my ear holes got really sore. Plus it is a pain to have to keep putting them back in properly to get a good seal again.
4. If you have waxy ears you'll need to clean them, a lot. (maybe that's just me
)
5. at a BGU event everyone who want to use them should have their own IEM's for hygiene reasons alone
Also Griff would have to take time to sound check each person to make sure they hear what they need.
IEM's are great but they can be a pain too. Like anything you need to balance the pros and cons. If the pros out weigh the cons then go for it because good ones can really help. I stopped using them at gigs when I was in the band just to simplify setting up and just ended up using them at rehearsals. Our rehearsals tended to be louder than gigs anyway.
Anyway, that's my thoughts.
Eric