Apple is releasing the Yosemite public beta today, which is pretty remarkable. It's been a long time since Apple has opened up an operating system beta to the general public. In the abstract, I think it is a fantastic idea. Developers are, generally, power users and bugs slip through that developers may never experience but would be obvious to non-power users. Jason Snell explains the details at Macworld.
All of that said, I don't recommend jumping into this beta unless you have an extra Mac sitting around. Even then, you have to be careful. Apple is making a lot of changes to iCloud and iCloud data is very much in flux right now in the betas. There be dragons.