We knew this thing wasn't going to be a speed demon and the numbers are proving it. Gizmodo ran a series of test on it. Boot time is 50% slower than a base model MacBook Pro and around 10% slower than the comparably footprinted base model MacBook. This is most likely due to the 4200 RPM 1.8 inch hard drive. When the SSD MacBook Airs come out, we expect much better results.
In other tests the MacBook Air faired better and even managed to prove itself the king of the MP3 compressing - which is likely attributed to its more modern processor and 800mhz front side bus:
