DVD and a wide range of digital stores including Direct2Drive, MacAppStore, Feral's WebStore, MacGameStore and more.
It will be out Winter 2011/2012 but we have not announced a firm date yet.
Edwin
You sir, are a legend. I own the collector's edition on PS3 and I'm more than willing to buy it again from the App Store! (even though I also have it on Steam)
I do have one teeny request though, if it's not too difficult, can you guys make it work with the Intel HD 3000 (even in a basic low-res 2D form, heck, even text only would be great) so I can play it on my Air? (well, not just me, but you know what I mean )
I can't wait to have a portable Mac OS X version (even if I can only play it on my MBP) Keep up the good work!
Also, Borderlands (also a port from Feral) runs like a dream on my Air (even with all the boxes ticked), absolutely incredible how you managed that. Major kudos!