As I said in the other thread, I support an OOC Room on a server that does not have a private room for each PC. That way there is always a place a PC can go and not have someone run across them and try to start a scene.
The only other circumstance where an OOC Room would be welcome is a server going the RPI route and not having channels. This ensures there is a place people can gather to chat OOC and make plans for meeting up on the grid.
I do support Private RP Rooms, though. They allow people to have backscenes off of the grid so people not part of the backscene aren't accidentally walking into the scene.