So, just checking to make sure, Do i still need to buy the game, if i have open beta client and the Lifetime Subscription?

I assume the answer to this is yes, of course, but i just want to make sure.

Yes, after September (6th?) you will have to have entered a Retail game code to remain in the game.

also, does anyone know if its gonna be sold on steam? because it says its out but theres nowhere that says 'buy now' on the page.

I've heard it will be sold on Steam however they may be waiting to unlock it till 10am PST since you can't get into it before then and that would allow Steam and Cryptic to avoid a lot of compliants on not being able to log in.

I have a semi-related question. I ordered from Amazon (package hasn't shipped yet... of course). Once I get it, will I need to re-install everything or can I keep the open beta installation that's partially patched up already?

No need to re-install just patch and go.

That's actually a good thread, and important information about the fact that we need to key in the serial number till 6th of september; I won't be at home before tomorrow, so was worried how much time will I have to get my code and type it in...

The beta client will suffice for the final game, btw :).