I'm toying with the idea, as my metal band are at the stage where we get to play venues where it's easier to run around a bit. Both guitarists have them and to be honest, neither of them really need one, apart from the standing on their own leads thing, as they seldom move from their pedal boards.
The singer and I are frankly, MUCH more mobile, and so I'm considering going down the wireless route. Not convinced though, and as the newcomer I'd have to find one that works with the existing frequencies we use.