This wouldn't help anyway. If the malicious party had access to alter the downloads (as they did here) they could just as well change the checksum shown on the page to.
>On the other hand, the Windows and OS X App Stores are awful.
Haven't used the Windows one, but what's "awful" about the OS X one? Quick, one click, installations, isolated, signed, easy updates.
Might be bad for the application developers somehow, but I don't see anything much bad about it from a user perspective -- except maybe the lack of trials. Then again I've been able to get a refund any time I bought an app that was subpar and written to Apple (that was 2 times).