OpenSolaris 2008.11 was just released for x86, it is a huge improvement over the previous release. I'm not really a desktop user but I think those features seem to be at least on pair with Ubuntu and other similar environments. It has automatic network management, Songbird, Compiz,Transmission, OpenOffice and a graphical package/update manager among other features.
On top of that it has a unique feature for the end users called "Time slider" which uses continuous ZFS snapshots to browse changes or restore lost data. It also has Netbeans 6.5, SunStudio, Ruby, Python, PHP and Java 1.6 available in the repositories making it an attractive choice for developers who now can utilize DTrace in a modern desktop environment.
This all is built on top of snv101b with ZFS as root filesystem with additional storage features besides ZFS (COMSTAR, iSCSI, CIFS) and virtualization (xVM, Solaris zones, VirtualBox).
The packaging system(IPS) has been long overdue, with OpenSolaris we now have network based repositories from which software and updates can be installed. You don't need to download all those packages yourself and resolve dependencies.
Take a peak here before downloading it here.
Perhaps it sounds like I'm working for marketing at Sun, but it's all that good ;)
Talks I have given
2 weeks ago