I can't speak of those particular ones, but I use an Sennheiser EW100 G2 for both mic purposes and live guitar use and have used the EW100 in ear setup quite some time back and they worked pretty well but in most circumstances they were overkill. I went to my local audiologist, sent $180 on some custom moulded 25db musicians ear plugs and they worked better in most all situations as I could hear everything clearly with almost no high frequency attenuation, there was no boom in my head when I spoke and I didn't need to rely on the retard behind the mixing desk to know what he was doing to bus out a mix for my set. Honestly they're great when you're playing for like several thousand people and headlining but otherwise it's just another piece of gear that could go wrong easily. Plus if you don't have an actual mix from the FOH, you won't really be hearing anything the other band members are doing which is a big negative.
I just replaced my old set with some new ones from Costco a few weeks ago and they are killer.