Downgrade is pretty simple, though it does require doing a fresh install of iOS 6 via DFU mode and then restoring your data from your backup. You can find step by step instructions via google.
As for non-dev use of the beta, it is technically a no-no and a LOT of people here get their panties in a knot whenever that sort of thing is discussed on these boards (torrents, jailbreaking, etc) so I won't go into details, but it is very cheap and easy to do... again Google is your friend.
Personally I see no issue with technically minded end users using the beta, as long as they are aware of the risks and challenges it represents; it WILL be buggy, it WILL crash (a LOT in early betas like this one), and there WILL be apps that don't work with it yet (either partially or at all).
This is all a result of the main purposes of beta software: 1) Find and fix bugs 2) Allow developers early access to update apps to be compatible with it. That said the more people that are using the software and reporting bugs (along with relevant diagnostic info) the better in terms of getting bugs ironed out.
Just be aware of what you are getting yourself into in terms of bugs, and don't freak out and post bad reviews of your favourite app that refuses to even run... dev's are not allowed to post apps that have been updated for the new OS until much closer to final release. So be prepared to live without incompatible apps until the fall.