I actually would not recommend a generic system for the simple reason that most manufacturers of these systems are really just selling transmitters and receivers, with the actual IEM's (ear pieces) are treated as simple give away, add-ons. Some of these IEM's are nothing more than glorified consumer ear-buds that don't fit well and don't offer good acoustic isolation which in turn forces the user to monitor at a dangerous level.
Not saying they are all totally useless for pro use, but consider this; If you do not have the same fit and isolation every single time, (which is almost impossible with ear-buds), the sound cannot be consistent from show to show. Then there is also the hit or miss factor where fit is concerned, everybody has two ear canals that are unique in size and shape........the implication of this in relationship to generic buds should be obvious, you do not want to spend you time on stage trying to keep your ear-buds from falling out of your ears.
I would suggest that users buy the best custom-molded IEM they can afford, and as pointed out above most musicians don't even need wireless system and would in fact do better running with a wired system. If you do need wireless, then choose each individual component on your personal (long term) need and budget. I find that when possible, mix and match can allow you to get a system more tailored to your needs than going generic. For the ultimate in hearing security, (and if budget allows) I would also recommend a high quality brick-wall limiter across the mix which can be used with wired or wireless systems. There are some companies (DBX, Rane etc) that are now marketing special, in-ear processor boxes, and although I have not used any of them, they all seem to be chuck full of unnecessary processing stages and are more complicated than they need to be.....more bling, more ways to screw-up the sound and more ways to screw-up your hearing.
Anyway, you might want to check out products from these guys;
Livewires, I've never used their products but I've heard a lot of good things about them, and their pricing for their pro IEM's is very reasonable and comparable with some overpriced consumer ear-buds.