This slashdot post summarizes pretty well what you gain and lose when deciding for a Macbook Air instead of a Macbook. Pasted here:
"Here's what you get going from the stock Macbook to the Macbook Air:
2 pounds lighter.
0.25 inches thinner, at its thickest.
Spiffy new touchpad.
OLED screen, meaning that the LCD should last longer (this is a marginal improvement)
1 extra gb of RAM, base (costs $150 to add to the Macbook on Apple's website, $50 to add after-market)
Trendy new computer that few other people have.
Here's what you give up:
1 optical drive
1 USB port
1 Firewire port (probably not a big deal to travelers)
1 replaceable battery (meaning that your travelers won't be able to carry a spare)
1 hour of battery life (even worse considering the lack of a replaceable battery)
1 ethernet jack (probably not a big deal, since wireless is slowly becoming ubiquitous)
400mhz on the low end, 200mhz on the high end.
Replaceable RAM (RAM starts going bad? Your Mac is going in for service. Hope it doesn't go bad after the warranty is up.)
Stereo speakers
Optical audio out
$600"
My Mario Kart Wii friend code: 2707-1866-0957
