It is beta thing really not vaild and how are you let developer testing software if it so unstable?
You are entitled to your opinion as am I, but please stop trying to convince people that a beta should be as stable as a released version. You can't compare Apple's beta to any other company's because you don't know Apple's intent. It's not a public beta for a reason. Apple may know and not be concerned if you can't, say, sync music on your development device because you are supposed to be testing your iOS apps against APIs. That's all. If you aren't going to follow Apple's recommendation on how to use a beta then you are on your own and your results will be disappointing.
In one way you are correct. We should stop saying, "it's a beta". We should be saying, "It's a private developer beta for your development device and how does <feature that doesn't work> affect the development of your app?"