You clearly use skype or another 3rd party voip system.
As much as I love the idea of "in-game" voip- the whole thing is run with the primary game thread; and absolutely messes up game playability. (plus no team-only integrated voip)
I believe voice commands are better; ya-they'll be abused but whatever, that is why you can bind you're voice commands with text and then disable the voice command sounds (if you want)..
The bigest advantage however, would be
vsay_area , since you could actually scream "GRENADE" to your comrades, and not disturb the entire team.
Also, flood protection to prevent spamzalots. Also queuing only a single "unique" voice command at a time would prevent FLANK spams that.