I'm sorry, but I wouldn't pay for being a beta user. Being a hacker myself, I commit a lot of time when I sign up for a beta. I report bugs, and give my opinion on what I like and what I don't like. In my opinion, a beta should never be the paid version. In this case, I'd say 'limited beta' is just marketing speak for an early bird deal. Which is OK, as long as you call it that.