I've been using OpenSolaris 2008.05 for about a week, and despite some small bugs, I really fell in love.
Until now I did not have the time to play around with Nevada releases, but OpenSolaris 2008.05 could really be my future #1 desktop (beside my Sunray...).
Things that worked so far:
-Getting Windows inside Virtualbox (yeah there are some apps still left running only on windows..)
-CentOS in a Branded Linux Zone (experimental Linux 2.6 support)
-Skype in a Branded Linux Zone(without sound yet)
-Zattoo in a Branded Linux Zone (without sound yet)
What does not work yet:
-TUN for Cisco VPNs
-ACPI (there are some drivers...)
-Sun Secure Global Desktop Client (at least the automatic client download...)
What's left to say?
Thanks to the OpenSolaris Community for all efforts.