Yeah, I got it sorted out. I pulled the frappliances from atvusb-creator and put them into the ATV finder in OSBoot of an eSATA drive I have for testing purposes and both showed up on the menu. Then I had to install XMBC Atlantis beta 2 and Boxee on my Mac, then copy those two apps over to the Applications folder. Works just fine with DVD rips, but as expected 1080p is way too much for the ATV to handle. If anyone is hoping for a Blu-Ray option for the current Apple TV it ain't gonna happen. The ATV just doesn't have the muscle for it.
The two movies I tried were copied over to the ATV's Media partition for playback. I wasn't able to figure out how to do networking to other volumes on my computers, so any tips there would be great. I tried the browsing like what can be done with Plex, but none of the volumes showed up on XBMC on the ATV. Obviously I'm not setting the network sharing properly - I just can't figure it out.