Apparently there are two models of solid-state drives in the Summer 2011 MacBook Air, a slow Toshiba and a fast Samsung.
You could read a bunch of articles stating how much it would suck to get a slower drive and then watch a long and slow video describing how you can check your MacBook Air SSD model. Or you can read about it.
Apple Menu > About This Mac > More Info > System Report > Serial-ATA.
You will see Vendor, Product, Link Speed and others. Below than in slightly bold text, will see something like like APPLE SSD. Whatever comes after that will describe your drive. If it is TS it is a Toshiba and probably slower. If it is SM, it is a Samsung drive and probably faster.
It may not matter which size MacBook Air you might have, the drives probably vary and there are good stories about getting them replaced.
Luckily, I got a Samsung 128 SSD.