It's also made very clear that you should only install iOS 8.4 on a device that you can live without, and that you are happy to completely erase if things go wrong. So you have nothing to complain about.
By the release notes, it is nowhere near beta. "Development" is whatever Apple has been building today, you definitely don't want that. "Alpha" is something that Apple would ship to particularly foolhardy people who want to be the first to try it out; "Alpha" will have serious known bugs. "Beta" should mean that you can run it except that there might be bugs that nobody looked for. There should be no serious _known_ bugs, but there can be unknown bugs.