Used to use Teamspeak on FFXI to talk to my LS during events and randomly, mainly just talked to 5-6 people though as it was rare to get more than that on the mic.

Typing in XI worked well because people actually seemed to have a brain, and things weren't stupidly complex when it came to mechanics unlike so other MMO's where you have to hold the keyboard in your mouth and play with your feet to avoid the doomray...

Talking is more personal IMO, some people like it, some don't. Me, I'll talk if I know the people well enough, but generally otherwise I prefer typing.