I'm running Suse 10.0 OSS on a dual xServe G5, 2.2 Ghz with 8 GB of RAM and 3x250 Gb SATA HD. It's a production web server and mySQL server. After getting through the whole PPC boot loader neurosis (how-to links reference elsewhere in this thread), it works like a dream. The el-cheapo video card I was using under OS X did need to be replaced with an ATI card (Radeon 9200) to get X running with respectable video.

Also, if you want to do NIC teaming look up NIC bonding. The dual gbit NIC's will team effectively once configured using the bonding stuff. On its own switch leg it screams.

Note: A heavily threaded tar task went from 40 hours to 12 hours on the exact same hardware with the same scripts by switching from OS X (10.3) to Suse. The talk I've heard about the advantages of Linux threading over OS X (ie. Mach microkernel) in heavily threaded apps (ie. Apache, mySQL, & especially Samba) appears to be true. There are signficant performance gains from a supposed increase in thread handling efficiency.