I'm rather oppinionated on the issue, so let me throw in my 2 cents (I know you're all gripping the seat of your pants waiting for it!).
ABSOLUTELY NOT.
You know why? Think about how many times you've been knocking someone around and they start calling you a hacker, or they start calling you a melee whore, or a beam whore, or a little -insert explative here-. Now are you going to suggest to me that you give them a way to complain through my speakers? Oh, I can mute them, but how many will I have to mute? And once I do, how can I tell what is going on between them and any of my other team mates or opponents?
Below Trunks introduced a novel concept... actually explaining through verbal communication just why you aren't a hacker. Have you ever watched a mother try to explain to her 8 year old just why he can't have that Power Rangers action figure? Oh trust me, there will be plenty of that on servers around the country if Voice Communcation is introduced to ESF. Besides... how can you communicate with someone who is screaming explatives? If you even get a word in, they'll just call you something else.
As far as tactical usage is concerned, ESF is a very fast paced game. I don't know how many of you are used to creeping through long dark hallways, hearing a few shots, and alerting your team mates. That's a good example of what Voice Comm is good for. What isn't it good for?
"Get that ****ing spamming f*ggot you useless noobs!"
How often do you think you are going to hear this?
Alright, now how about this:
"He's in the corner of the map, charging up a final flash! You come in from the left, I'll circle around and drop a flash grenade... get ready!"
You probably wont hear something like this, because it doesn't fit into ESF. In ESF, when you see someone charging up an attack, you either run, or rush. You don't get on the phone and ask if it's OK, because in the time it takes you to get confirmation that thing will have been fired off. Another thing people think they can do with it is alert their team mates to incoming blasts... this too is novel, but nearly impossible. Beams don't travel all that slowly, believe it or not. Even a final flash can make it's way across a map in a few seconds. Pressing "C" and screaming "FINAL FLASH GET OUT OF THERE" is only going to hurt ears. Nearly everyone will see something that big coming at them in the first place, and we don't need 3 people competing over the comm screaming about it. I certainly wouldn't want to hear "Where the **** were you f*gs!?" every time an inexperienced player gets angry.
You guys have to rethink ESF's goal. Are we trying to be slow and tactical, or fast and full of ourselves? I think the latter, don't you?