The last release of OpenSolaris dates back to July 2009. The next release was scheduled for March 2010, but Oracle did not release anything. It is dead silent around OpenSolaris.
On 12 July 2010, the OpenSolaris Government Board sent out an ultimatum to Oracle: "please communicate with us or we will resign and hand over the little power we have back to Oracle".
These are all signs that OpenSolaris has no real future. And think about it: what is Oracle's interest in OpenSolaris? Maintaining an operating system and develop new features is extremely expensive. What is their benefit? I can't see any. Sun was a hardware manufacturer and promoting OpenSolaris made sure that people got experience with the operating system that powers their hardware.
Unless your environment already consists of Solaris-based systems, as of 2010, there is no reason to use Solaris any more. OpenSolaris was, until recent, the only operating system that supported ZFS natively, so the only choice if you really wanted to use ZFS. Now FreeBSD has native support for ZFS too.
For the people who are fanatical about ZFS this is great, because it would be a shame if ZFS could only be used in combination with a dead operating system that supports less hardware than Mac OS X.
But I see no future in OpenSolaris and you should think twice about running it, either as a production platform or at home. Use a platform that has a large user-base and a big community.
I think that if you are running OpenSolaris, you must start thinking about migrating to FreeBSD or Linux, however painful that may be.