I agree with Ken that this RC has a good chance to be the last one before the final release of FreeBSD 8.0 (there were only minor changes between RC2 and RC3).
For all those who didn't follow the development of FreeBSD 8.0, here's a very short summary of the improvements introduced with the new major release tree:
- ZFS upgraded from v.6 to v.13; no longer considered as experimental feature
- Lock-free TTY layer for better SMP performance and scalability
- Completely rewritten USB stack (the only part of the kernel that really annoyed me with its suicidal tendency)
- Better support for the GPT partition scheme
- Multi-IPv4/v6/no-IP jails