I'd say just buy it when you can. But you might want to wait until the final version is released. Because Notch stopped grandfathering people in to the future releases after the beta came out (if you got it during Alpha, you're fine though).
Originally Posted by ~Spacial_Rendation~
Rules of fansites:
1 - You can either be right, or you can be happy.
3 - If you think someone is lying about being an expert, they are.
5 - If you think someone is lying about knowing people who work in the industry, they are.
14 - There's no such thing as a source that isn't one-sided.