"In exchange for dramatically lighter weight and an extremely thin profile, Apple has definitely compromised when it comes to the MacBook Air's tech specs. And the results of Macworld Lab's preliminary tests of the MacBook Air reflect those compromises. For this first set of tests, we used a default-configuration MacBook Air powered by a 1.6GHz Intel Core 2 Duo processor with a 4200 rpm, 1.8-inch 80GB parallel ATA hard drive. The MacBook Air's processor clock speed lags well behind current MacBook (2.0GHz or 2.2GHz) and MacBook Pro (2.2GHz, 2.4GHz, and 2.6GHz) models, and its hard drive is also slower than those used in the other models."
They also needed to buy a WiFi adapter and an external USB Optical drive to proceed with their tests, which adds to the already rather steep price.