At one point we peaked at 193 simultaneous users. There were 45 users in the voice conference, with one user speaking (the rest were muted). Shortly after 193rd user joined, we tried to upload a new presentation and the server stopped responding.
Earlier, we tried opening as many web cams as possible. We achieve 20 simultaneous web cams in a session.
We're very happy to see BigBlueButton 0.71 support this many users on the server at once.
Keep in mind, we don't recommend to anyone to run BigBlueButton with 193 users in a single room, but to know it's possible was pretty cool.