Sealed tight like an iPod, nothing is (officially) upgradeable. Even the battery is not replaceable. Anything goes wrong, you have to ship it out for repairs.
It doesn't have a network port. - Not really a big deal. However, if you do need it, you'll have to buy the USB-RJ45 converter of Apple (which costs quite a bit for a wire peripheral).
On the looks department, well, looking at it from the pics, it just resembles a very thin Acer Gemstone. Only when I get to see it physically will I change this view, I guess...
The price.... US$1800 is a bit too much. I thought they were going to price it 'competitively' as from the rumors? Oh well...
In the end, I think this laptop is for those who have too much money to burn ala Paris Hilton. Me, not only am I not qualified to be one of those, I also am not impressed with the device (READ: device, not computer).