As one who has done all sorts of sound for years, I was troubled by the lack of attention paid to the key words, "Open Mike" and all of the attention paid to a headset as opposed to a lavalier (lapel) system.

Lets deal with the first; Open Mic. To properly set up a wireless system you have to do a fairly comprehensive but not particularly time consuming sound check. With a true diversity system you can still have drop-outs even at the stage and if the venue has a fair amount of florescent light or dimmers, you need to know that the sound man has RFI/EFI systems up to the task. UHF is definitely the best, but more modern systems are "frequency agile" instead of fixed-frequency systems (which can take care of picking up or sending out interfering signals). And the Europeans are far more unforgiving of non-licensed mic systems, so you go onto the list of Usual Suspects and may actually be required to show your license at the concert. (Don't laugh, It happened to me in Ireland at the Fleadh).

On the other hand, the idea of a wireless system for your guitar actually makes more sense because you can reduce some feedback problems if you set it up right. And as mentioned above, you can more easily "play to the mike" with your voice than with your guitar.

As to headsets, a good lavalier system will be far less expensive, some are not even wireless and can connect directly to an open line to the stage with little adjustment problems at the board, and in the case of the lady with the lap dulcimer, she will be singing directly into it without all of the paraphernalia that goes to it.

Remember that to use a wireless system you will need to arrive early, make certain you have a separate power source for the receiver, a line that connects to the sound board or (God Forbid) sound box, provide either TS/TRS or XLR cables from that receiver to the sound board, plus the room to set the box and its antennas up somewhere in the open to receive the signal from your mics. You will need to put in fresh batteries into the mic, and then you will need to "walk the room" at least to the stage and it's four corners to find out any "drop-out" spots. And during your performance you will need to remember that even if you have a switch to turn off the guitar wireless, you will also need a switch (which ARE NORTORIUS) for switching from the "mute" to "power off" bypassing the "on" button to your head set, while you tune. The end result is that when you again turn the headset mic on, it may be in "mute" or "power off" position. Then you're left literally scatching your ass trying to get your mic back on.

Or you can leave the mic on and signal the sound man to mute your channels while you tune (always a Loss Leader at an Open Mic). And if they are using a board that does not mute the monitors at the same time, you just might find the room harmonic that blows the speakers while tuning.

Don't get me wrong; I use wireless all the time and at the proper venue they are amazing. This week I gave Santa Claus a wireless hand held with a Beta 58 head and a windscreen and he bellowed "Merry Christmas" a block away from where he got out of the sled to a downtown area running eight 15 inch speakers on poles. When he drove the Gritch out of the Courthouse (a local custom) Santa was able to invite all the children to sit near his throne until each child was heard (for blocks).

All I'm saying is, look at your concept: you're going up to a stage in a pub to play a set of songs at an Open Mic, and then getting off the stage to put away your guitar and listen to the others while enjoying a pint. Where I come from, "that dog won't hunt", with what you need to attend to, using wireless.