I finally got a 2-seat system working reliably on dual ATI R710's (Asus EAH 4550s) this afternoon, using F10. The stability problems I mentioned earlier cleared up when I reduced the set of services running -- the important stuff (dbus, NM, hal) are all still enabled so I need to do some more checking to find the conflict (isdn? bluetooth?).
More tests to follow, but it's encouraging to know that there is at least one Open Source driver that can be used to build a multiseat system with the current X server. I'll blog details in the next day or two.
These are my first two books: X Power Tools, a thorough guide to the X Window System (O'Reilly, ISBN 9780596101954) and Fedora Linux: A Complete Guide to Red Hat's Community Distro, a practical hands-on book on Fedora (O'Reilly, ISBN 9780596526825).
Fedora Linux is also available for online reading through Safari and in downloadable PDF format from oreilly.com