I bought a Cinema Display for my 11-inch Airbook.
The display is great, as I expected, but what keeps striking me is how the Airbook (sorry, "MacBook Air") running this huge display doesn't feel at all like a compromise in power. Sure, I haven't tested big photoshop or video files, but certainly with day-to-day work it's not only adequate, it's quite zippy. Just a delight. They say the processor itself is modest, as befits the tiny 1-kilo frame, so much of the nimbleness must come from the solid-state drive, I guess. Anyway, it's nice. It runs totally silent, and of course when I unplug it, it's the ultimate in portability if you want a full-sized keyboard.
It's seen here running lid-closed, but if you open it you can use the external screen either as mirroring the built-in screen, or for extending the desktop.