That Dell is half the price, but twice the weight (at almost 4 pounds!)... and don't forget to add the groovy webcab option for $79 (built in on the Air). I wonder also how much it would be to upgrade the Dell to a solid state drive?
Also the Dell Inspiron M101z uses a AMD Athlon™ II K125 (1.7GHz/1MB cache) cpu, while the Air has 1.4GHz Intel Core 2 Duo processor with 3MB on-chip shared L2 cache and an optional 1.6GHz Intel Core 2 Duo processor with 3MB shared L2 cache; does NOT include SSD as an option; has 2GB RAM DDR3 SoDIMM at 800MHz with no option to upgrade to the faster Air 1066MHz SDRAM and; uses the AMD RS880M chipset with SB820 south bridge as opposed to the Air's NVIDIA GeForce 320M.
The closest Dell offering is the Latitude 13 at $1009.