Here's a list of (small yet noticeable) differences I've compiled for the new MacBook Air in no specific order: The SSD unit is a mini-PCIe card instead of a standard 1.8" SATA unit. No backlit keyboard. IR sensor and sleep light have been omitted. 11" has reduced size function keys. Power button is no longer aluminum and takes the place of eject key. Last row of keys on 11" are of same height as alphanumeric keys; the last row of keys on the 13" are slightly taller than its alphanumeric keys. 11" uses ultra-low-voltage processors. 13" still uses low-voltage processors. Stereo speakers in both models. Lower operating temps and fan speeds. An explanation/opinion of each can be found on my blog post. http://doesntexistat.blogspot.com/2010/10/new-macbook-airs.html Hope this helps! If you notice some more minor differences, please post!