Later betas are usually pretty solid. Early betas are usually absurd messes - iOS7 beta 1 was, IMO, nearly unusable.

I wouldn't let any early Apple beta anywhere near a critical production device.

Depends on the update but the early betas have noticeable problems and crashes, in my roommates experience. Plus, wiping the hard drive and doing a clean install of the final new OS can be a pain

My hope is that these will be a bit more stable than a typical apple beta since it's public. Many of the early betas for iOS feel like alpha quality because they're being shipped out to developers who aren't supposed to use them on a primary device (even though we do). They remind you to make a backup, but are probably (hopefully) operating under the assumption that people are going to be installing them on their main machines.

I just updated and noticed no changes. Seems to be very stable so far.