Which one to buy?

[DrSteam]

So I'm confused. I want to buy this game. The new standalone game is out next week, which doesn't require the original game. But if I buy the new edition, will it be compatible with the current edition? Or should I buy the older version? Its not really clear on the website.
EDIT Just found a forum thread implying that it is a standalone addon. So I'll rephrase the question slightly. Are most of the arma players here getting the new expansion? If so I only need to get the one game.

[Blunt]

I did read/hear that the new standalone is backward compatible with Arma2, so you'll be able to play all the old maps etc.
But someone who really knows their onions will no-doubt be along in a bit to put you right.

Edit: I will be getting the new one

[Benny]

My understanding was that the new one was backwards compatible. Let me nose around and find out...
In terms of all buying the new one, I would imagine that yes, over a period of a couple of weeks everyone will.

[Benny]

Yup, looks like you can buy the new one.

I'll defer to Tobius as to how we may or may not phase in the new features.
http://www.offdutygamers.com/2010/04/meridian4-acquires-rights-to-arma-ii-operation-arrowhead/

ââ,¬Å"We are excited to partner with Bohemia Interactive to bring these two outstanding offerings to gamers,ââ,¬Â said Steve Milburn, Marketing Director, of Meridian4.  Ã¢â,¬Å"With new playable content and new simulation features, ArmA II : Operation Arrowhead is a robust PC game that does not require the original ArmA II, yet is fully backwards compatible, so owners of the first game can enjoy the new features and a whole new experience.ââ,¬Â