Well, following Blizz's newest patch there will soon be some kind of voice chat enabled at sometime. Their info on it sounds good but I'm worried about some of our dialup members. I'm not sure if the codec Bliz is using will saturate their connections or not. It would be nice if it doesn't so that way I can get everyone in a raid to hear me while I lead the run since some of our members haven't taken advantage of our Teamspeak server.
If I find that the new voice chat feature does cause problems, I will stick with Teamspeak for our raids. I prefer Teamspeak since I can administer it in the event of troublemakers. It looks as though Bliz allows moderators on the voice chat though so I will be able to do the same thing there as I do in Teamspeak.