I always had problems with my Teamspeak 3 client application on OS X. The overall performance was very poor. Not the sound, I heard everbody loud and clear and I wasn't lagging too but everything else like switching channels or even just selecting them took seconds!
I think I've found the solution to this problem: Unicode characters
Maybe not all but several special characters causing the application to significantly drop performance. The problem was mentioned in this thread on the Teamspeak forums but they didn't found a solution though they gave me a hint.
I used a special character in almost all channel names on my server as separator. The character in my case was
⁞ (info). After I've removed all these characters my client performed noticeable faster. The only downside is that you need to be able to rename the channels in order to solve the problem but hopefully they fix it soon.
This is a little demonstration I've put up for the TS3 support: