The aftermath of the roll-out of voice in SL is still being discussed at the forum (November), this thread goes for 12 pages (online here for folks with SL log-ins).
It seems voice is a ‘bigger deal’ in SL than in WoW, but not as big a deal as once feared.
The contributors to this discussion (who may or may not be representative!) seem to agree that voice is less of a change than people thought it would be. Many prefer not to use voice (or prefer to use it sparingly) for technical or other reasons. Other people say they like it alot. There are some (hotly contested) remarks about RL men with female avatars being ‘outed’ by voice (ie the assumption that female avatars not on voice, hide a RL male). No-one identifying as deaf took part in the thread. There are a few comments stating that ‘voice is good for education and business communities’ which rather assumes that such communities are for hearing people.
All in all, the discussion implies that voice has not had a uniform impact across SL but that practices in particular situations have changed – So, in some contexts, voice might now be the norm, but not in SL as a whole. That’s my impression, but it’s hard to judge this just from walking around SL. Voice users are indicated to one another, but not to us non-voice-users (hmmmmm, is that fair?). I do walk past groups where there is ‘text silence’ but perhaps they are IMing….about me being a bloke in RL.
Here (August) is another 7 pages on the topic. Sheesh.