I perform pretty regularly, and I have tried tons of wireless units, including the Line6 stuff.....which I don't have a high opinion of. During the time I used those I experienced constant drop-outs, and to be honest I didn't think they sounded all that great.
The Shure GLXD16 is what ended my search.
I have used mine on countless gigs, and it has been 100% rock solid, no dropouts, easily rechargeable via USB...and there is even a courtesy USB outlet on the receiver unit, looooong battery life, metal casing.
Oh, and did I mention the receiver unit is also a fantastic tuner...as good as any tuner pedal I have tried?