Screen size, backlit keyboard, matte screen option, faster processor, still better (but not that much) graphics, better speakers, and more...
I can see your point w/ the screen size, faster procs, etc., but I'm sure some people would still be saying "These features are available, why don't we have them in the Macbook?" To me, it seems like quite a few people want all the latest and greatest technology for $799. While that would be nice, it's not currently possible and they have to realize that and stop complaining about it.
They know if the iTunes CoverFlow scrollbar is blurry, and if Disco and other apps are not fully supported because the graphics suck, and if they can't connect to a 30" monitor.
iTunes, I understand that. I've never heard of Disco so I don't know about that. For really intensive games, yeah it'll suck. Less intensive games should work well enough. 30" monitors would probably be too much for the average user. IMO, if someone really needs a 30" monitor, they'll probably need the power of a MBP.