When used correctly and sensibly, in-ear monitoring can greatly benefit the sound and performance of a whole band, and eliminate the risk of long-term hearing damage. However, in-ear systems can also cause hearing fatigue and even damage remember that they are actually small loudspeakers placed literally millimetres from your ear drums. To this end, it is well worth investigating a system with integrated limiting (or adding a limiter into the signal path) to catch the transients associated in particular with the snare drum and cymbals and reduce their effect on your ears.
As with any other piece of new equipment, it is advisable to try an in-ear monitoring system a few times in rehearsal before gigging with it, as it can take some time to get used to them and find the settings that work best for you.
There is a little more to in-ear monitoring than first meets the ear!