I always used pushed to talk and never had a problem. I set it to my middle mouse button, and made sure nothing in CRPG controls was set to use "Mouse 3" or whatever.
Voice activated is bad, as you use it longer and longer the probability that your friends hear you jerking off/getting owned by Dad/talking to your cat/ etc. reaches 99.9% chance of occurring.
Also it's really annoying when that one guy is just breathing heavily playing Skyrim or whatever and you have to move him out of the channel AGAIN.