NS2 is coming and we have several candidates for the voice communication standard of NS2. Ventrilo 2.1 doesn't work with Windows 7 properly and is not getting updated anymore. Sooner or later we have to switch.
The newest Teamspeak is very easy to setup with the wizard which is even easier than in Mumble. Servers which are for non-commercial purposes can obtain free license to host unlimited clients. It has huge number of features, some of which are useful (such as per-client volume) and some which are not (3D sound). Only downside I can think of is the lack of comments, but you can send text messages to channels. Other thing is the huge number of features which clutter the menus a bit. This is my personal favourite for next generation voice communication software for NS2.
Mumble 1.2 is the newest stable version. The voice, atleast in earlier release had occasional glitches and the password-system (token system) is unintuitive. Both TS3 and Mumble use the same CELT voice-codec which is very clear albeit adding a bit of metallic sound (barely noticeable in TS). Biggest drawback is probably the engineer type of user interface (mainly settings, other menus are good). Also some reported problems with NS losing sound but this was fixable. Mumble has in-game list of nicks which is useful in gather where you may not know whos talking.
Shockvoice is yet another voice communication client which has many more-or-less useful plugins. Its rather easy to set up, but requires .NET which most computers have nowadays, but is a big drawback for those who don't.
Well we all know Ventrilo, and its newest version. Great features but commercial. Hosting costs strawberries. Since we already have the network and CPU capacity to host voice communication server on our own hardware, its unlikely we're going to host any Ventrilo 3 servers. If NS2 would bring up new players, it'd be the admins and donators who would have to pay for any extra slots required (now it would be 50-100 euros per 6 months).
Currently there is a TS3 server hosted at: ensl.org