Scrolling
So many threads along these lines....
Also quite subjective, because as with most Apple products, how you FEEL about it seems to really matter. Apple kinda getya, dont they
My 2pence...
The 11" is an absolute babe. I have a 2010 model, maxed 2012 should arrive on Friday/Monday. I will have my sole machine in a tiny frame.
If the battery life is of real concern, fine, go with the 13" (and stop drooling over the 11

)
But if its not, (and it never has been for me because I am never far away from a socket, and frankly my choice is to have the small sexy machine even if I carry the charger), then consider carefully the "additional" scrolling apparently required on the 11"
Again, I am interested in real world experience here, because for me its NEVER been a real issue. When I am reading my two fingers naturally lay on the touchpad, and OK whilst I may have to scroll the screen 17.2% to read the same as on the 13", it feels natural. Your eyes can only read a small vertical amount at a time anyways..
Sorry if it doesn't necessarily help much, but my tuppence. Overall I'm happy to live with the apparent weaknesses of the 11" (battery and screen estate) because using, carrying, opening, using the 11" is an absolute joy.