We have been hammering away quite hard on OpenSim in the last while. I posted some notes about Top 10 Issues we see as of today over on the Rezzable.net blog. I probably missed something really obvious, irritating, but hey, 10 is a random number. Short summary: "In general OpenSim has come quite a long way in the last year. There is still quite some road in front to get it to be a sort of 3D Web Server like Apache. It is very complex--maybe too much so, but nonetheless it works. And it works a lot better than it did a year ago."

Also check my older post from last time we updated on OpenSim.