The Macbook Air is definately an impressive piece of engineering.
Sure, it has no optical drive. That's to be expected. I think I'd like my current subnotebook even more if it had an optional/removable optical drive, or even none at all.
The lack of an ethernet port is harder to forgive, however even without one it would only represent a minor pain in the ass (for me) based on my current laptop usage patterns.
However the sealed battery? Ouch.
If you're interested in Steve Jobs' Macworld keynote, but don't have an hour to spare, then check out the 60 second version. Better and better and better.