I couldn't agree more.
I've actually picked up one of these myself, and am looking to mod it. Going is slow so far, I'm trying to find a way to make basic updates (adding an rc script that writes output to a file), and test them, without having to remote the drive to read it every time. After all, the more times the macvision is taken apart, the more likely a ribbon cable is to snap.
Simply reading the drive is easy via USB, however it's currently being mounted in ro mode. Without an easy to read fstab, I'm not sure where it's defining that the "mp3" drive should
be mounted rw, and the rootdisk ro.
First impressions: http://www.icewave.biz/macvision
I'd really like to have some form of a USB console or something, but I'm not there yet. For now, I'm picking up a new HDD this week so I can do a complete mirror of the drive should I blow it away. I'll keep trying to pour over the filesystem as time permits.
I've also been trying to get several ARM emulators up and running. Simply having a chrooted ARM environment of the filesystem would help a lot, especially when tools such as ldd become available.
Anyone else working on this? I'd love to collaborate with someone...