What codec are you using with Teamspeak?
It's pretty flexible and some of the codecs sound better than phone quality. I've always used teamspeak without quality issues, except when some moron has his mic right next to his speaker and voice activation enabled and we get infinite reverb because he's playing the voicecomm right into the mic.
Personally my server is setup with Speex12.3, and it sounds great. But the default if you create a new channel is often some horrbile 5.x codec that sounds like ass. So if your admin doesn't have his server setup right, you might think TS totally sucks, when really it's just whoever is running the server (or whoever created the channel without selecting an appropriate codec)