I'm not a developer, but I did get a "by invitation only" thing, so I am on developer betas (though when I installed, it was labeled as "public").
For a first beta...I'm actually surprised. Battery leaves a bit to be desired, but I expect that this early. Honestly of the bugs I've sent feedback on so far...the most annoying ones are the notification badge on my Settings app despite not having anything in there that needs to be addressed, and that the default iOS 14 wallpapers seem a little washed out. Ever since I downloaded on Monday, I've been kicked out of an app like twice total.
Is it on my daily use device? Yep. Phone and iPad. Despite receiving the invitation for macOS, I didn't (and won't) jump on that one. I need my MacBook for work. In terms of daily use, the biggest gripe is the battery, but again, that's expected. I'm pretty satisfied so far to be honest. I will say though that what seems to hit my battery the hardest is listening to music, even with the screen off. That hits it a little harder than even Facebook does.