I first heard details about OpenSolaris at the ApacheCon Keynote by Andrew Tucker (Streaming Video of it!). I walked away from his presentation believing that at least the Engineers at Sun wanted to make Solaris Open Source work. I was also quite impressed by Zones, and the capabilities it brings to server admins. Hopefully FreeBSD's Jails will get some of these features.
I still wonder if OpenSolaris will explode into a great community, or fall flat on its face. It is a great experiment on Sun's part, but, I am not sure they are prepared to let go of control. They still maintain a firm grip on everything that happens with it. Its not open version control. Then again, neither is Apache. Sun's great challange will be giving out commit access. If they do this too slowly, people will leave the community. If they do it too quickly, the quality will decrease.
On another note, I do not want OpenSolaris to just take a Linux Distro's userland and ship it on a ISO. I would much rather have a FreeBSD userland. What could be better than Solaris 10 Zones, with a FreeBSD userland?