I installed Beta 5 today and started working on a test course. I managed to make a course, create a module and then went in and chose to add a Text & Media lesson. The problem is, I can see the pretty html layout, but there's no side bar, and saving does nothing. I have to just cancel out to get back to anything. I tried this in the newest versions of Chrome and Safari on a MacBook Pro running 10.10.1.
I'd really love to start actually building a course, but as of now, I'm stuck.