1.) respectable processor speed
2.) FireWire 800
3.) built in optical drive instead of an extra cost item
4.) backlit keyboard
5.) normal hard drive space
6.) 4gb of ram, which is the minimum anyone should have these days. The OS takes up a gig by itself.
To me the air is gimped in many areas just to make it thin, new, fresh, exciting. The geekbench score for the 1.8ghz is 2766. Sad. The hard drive storage is minimal at best. What good is a thin laptop if you have to carry around external drives in order to store any real amount of data and files?
It's the netbook of the mac universe. And that's fine, and good for most facebookers and twitterers, but for any real work or usage, the MBP is the way to go.