First impressions, the keyboard is strange. I'm not really sure how to describe it, but it feels very different then my MacBook Pro. Also the touchpad has a slightly rough surface, instead of the really smooth surface on the MBP. The magnetic latch is pretty cool. The screen is very nice looking, a very good upgrade over what I saw on the iBooks. Very bright, crisp and a decent resolution for this size.
They are selling pretty quickly too it seems. The local Apple store here in Austin sold me their last 1.83 unit, and tons of people were crowded around the show models contemplating one. Looks like a great hit for Apple.
Now to see what they do for the PowerMacs. I'm sure Apple can't wait for Intel to release the Core 2 chips.