It's not like a beta operating system where your whole system will be messed up if something goes wrong.
I mean Yves isn't going to accidentally destroy a whole piece of software in the small scale updates from 248 to 249. Plus if you have the appropriate backups being saved, theres really no chance of you accidentally saving over a project that suddenly is messed up because of a new build.
Really, I don't see why anyone would be afraid to use the new beta's of MMF2. I mean these beta's are more about feedback then anything. There's no real risks involved.