We have investigated, played tried and tested numorous modes, with the help of our friendly local Guitar Center and the baseline is, you get what you pay for! I.e. a $49 TX/RX will work until someone comes across with a cellphone, heart monitor or a little kid flying his remote plain in the area! Going the Shure way is the sure way.
OK, it's more expensive, but the interference level is close to 0, if not 0.
One more thing, if you do want to use it, ALWAYS keep cables at hand, and ALWAYS go for UHF TX/RX on which you can change the frequencies!