FWIW, I've adopted Moodle this semester to replace our institutions's use of BB. I'm beta-testing it for 7 classes, 2 of them 100% online, the rest with regular lectures but with all homework, testing, grades, etc.. online.
Our school has 8000 BB users, and so we still have to figure out how many Moodle could handle, but you couldn't pay me to go back now, even with the problems I've had (which seem to be unique to posts getting confused with IE on the first go-round).
So as my brother used to say, "Go to town!!"
d.i.