I used OS X 10.9.3 public beta when it was released..
I did run it native which is usually a bad idea, because crashes, app etc can result. You typically download an app and install it, which allows software update to also download betas.. this will allow download of the beta 10.10
u can easily uninstall the app. but any beta's u already have installed as a result will stay installed (e.g safari betas as well ). This is why u shouldn't use it on main system.
If possible, run it on another machine, not a production machine you use every day, since with beta u dunno whats going to happen..
I think you can't upgrade to full release, the whole idea is to test it, so makes sure u have a tie machine backup, since you'll need it when the times comes to install OS X 10.10 when its available.