I’ve installed the first developer beta of each major iOS release since they made it so you didn’t have to download the beta from the developer site, and I’ve done the public betas before that, as well as the iOS 7 developer betas.
Always on my main/only iPhone, and I’ve never had any major issues or any data loss. Some were buggier than others (iOS 7), but at worst, it’s just graphical glitches, minor features not working correctly, or rarely an unimportant app not launching.
This beta is probably the least buggy one. Springboard has only crashed like twice so far, no app issues at all, and just a couple minor glitches (icons on the Home Screen wouldn’t move where I wanted them to, but I eventually got it to work).