Originally Posted by AaronP
It's not a hard and fast rule, as became obvious with the recent 1.10 cycle. In any case, we still don't officially support RC or prerelease X servers. The advantage of freezing the ABI ahead of time is that we can build a driver and start it through the testing process before the final server release. The problem we had in the past was that we couldn't assume the server ABI was frozen until the day of the official release, which meant there was a delay that caused headaches for people.
Xserver ABI version is frozen in Ubuntu 11.04 (final version released) with X.org version 1.10.1. Please build the driver series 96.xx.xx.