since new versions of teamspeak and mumble has been
released lately i wonder what voip you prefere to use?

my personal preference is

1. mumble (low latency)
2. ventrilo 3 (best quality)
3. ventrilo 2.1 (most used)

here is a nice test of delay in a couple of voips
http://www.youtube.com/watch?v=qMfF36NvoJc