I've decided to try to make the switch from the proprietary fglrx drivers to the open source ones. Everything works great, but I've been noticing a lot of tearing during video playback. I've noticed it works slightly better VLC than XBMC, if means anything. As far as 3d; it plays Minecraft fine on the highest settings. I know that's not much of a benchmark, but they are open source drivers that supposedly have not 3d acceleration. I was wondering if there was a setting or something that could be done to improve performance. I am running Debian Sid with the Linux-libre 3.5.2 kernel. The card is a Radeon HD 7970. Thanks.

Could you tell us your mesa version?
AMD Radeon 7xxx series basic support has been recently added to mesa, so you'll have to be patient for proper 3D support...

I've tried with Mesa 7.11 and 8.04. There doesn't seem to be a difference in performance between them.