I personally have not used Gentoo on the desktop, but I have friends & coworkers who have, and they have been generally happy.

Arch is awesome, I am not currently using it but have used it before.

Another possibility you could look into is Debian Testing. Debian has the reputation of including "old" packages for the purpose of stability, but the "testing" version of the OS is much more up-to-date, and if you need something even newer, and are feeling adventurous, you can install specific packages from debian-experimental.