Before switching I used the original Series X ThinkPad. A 3 pounder, but fantastic for business travel - especially at my age. I strongly believe this type of form factor would be a huge hit - especially in the education market - and might provide for a very attractive price point. Being able to attach to an external display would also be important - my current 15" PB is attached to a 23" display when I'm working in the office. The range I would look for is:
MacBook mini
MacBook (iBook)
MacBook Pro
If all used the Duo from Intel the above would result in an awesome line that would be hard to compete against - especially if all had iSight built in.