wireless headphones:
The Green Hornet hit the highlights. Also, don't even expect to be able to really hear them above loud sources without damaging yourself. Don't expect to get a good idea of the true noise or noise floor in your tracks with the current crop of wireless headphones---and I wouldn't count on a reliable mix with them. I don't use them on most (condenser) mic work because they do bleed into the room. I use them but I depend upon my Koss, Fostex, and Extreme Isolation cans.
That being said, and if you keep their limitations in mind, they are convenient if you're doing a line track and you need/want the freedom of movement or comfort.
Battery time on some is exceptional (Sony sets can run for over 20 hrs at a time and you can self-install a higher mA-hr NiMH battery for any "let's drop acid and jam for days with the Dead in the desert" sessions---but that's another story.
Good luck,
Paj
8^)