I stopped by the Apple store today to pick up a repaired computer and test drive Lion on the new Macbook Air. There is a LOT of animation lag with Mission Control with these laptops. This wasn't just a little lag, like I saw on the 15" Macbook Pro, but rather a huge amount of lag. Trying to drag a window from one desktop to another had a 2-3 second delay. Overall, Mission Control and even Application Expose do not work at all on the new 13" Macbook Air. Animation is very, very jerky or is missing all together. The 13" comes with 4GB of RAM on all models, so RAM is not the problem. I would recommend that you try one out in the store before you buy it to make sure it works for you. edit: Actually, I didn't confirm that I was using the new Macbook Air. Hopefully I was using an old Macbook Air.