Every day, several new revisions of OpenSim are committed to the subversion repository. Bugs are fixed, new directions are discussed during office hours or on IRC; there's limited but official involvement from IBM, and obviously Linden Labs is aware of Opensim, and talking with OpenSim people too. Things are happening, and much progress is made.
This wouldn't be surprising if Opensim were carried by an active community of dozens or hundreds of developers. But if you check out the project stats, it's really quite a limited group who's actively contributing code. They are doing a good job and deserve some public praise.
So, here's to the opensim developers!