No, the App Store is the number one store for computer software, even though it only runs on Macs. More people buy from the Store than from Best Buy or Amazon, period. Much more impressive.
(At least, that's what Jobs said.)
It was kind of obvious, wasn't it? They're releasing the unfinished developer betas through the Store, and phasing out boxed software. Anyway, it'll be awesome to get the new OS with just a few clicks and have it install automatically!