Alright, here's the deal. Lots of misinformation from both sides.
iOS 5 and iOS 6 both had a relatively smooth and stable beta process. It's likely that iOS 7 will continue this trend. I know I personally had zero major issues with either iOS 5 or 6, even in beta 1.
Either way, you are assuming a certain amount of risk by installing a beta version of iOS on your phone. Apple is not responsible for any data loss that may occur, nor are app developers responsible for fixing any bugs that pre-release iOS 7 users may experience. If you install iOS 7 beta 1, expect a very good, polished experience- but be prepared for bugs and app crashes everywhere. We just don't know at this point.
TL;DR- Install iOS 7 at your own risk. It's probably okay to use, but don't get upset if it isn't.