I love my new MacBook Air 11". Used it for most of my flight from Atlanta to Chicago today (about 1.5 hours flying time), and for once didn't have to worry about the guy in front of me leaning his seat back all the way into my lap. Also had a reported ~5.5 hours of battery time left when I had to shut down. The only thing I would do differently next time is get maximum RAM (currently sporting 2GB versus a potential max of 4GB).
When I'm at home, I run the MB Air in clamshell mode connected to a 20" cinema display (old school, baby; that's how I roll). Works great, everything displays where it should in either mode.
There's this one app, RSA SecurID, that I occasionally need to connect to ThoughtWorks' sites. And it is decidedly not smart about repositioning itself. I usually have it dragged down out of the way, to the bottom right corner of the cinema display, but today while traveling I found out it always stays off the screen, even without the cinema display connected. Exposé will show it to me when I switch to the app and Show Application Windows, but when I click on it, it zips back off to the (now non-existent) bottom right corner of the cinema display. Restarting does not help, nor does gathering windows nor detecting displays in the Displays settings panel.
So I had to resort to opening the .plist file for the app (located for me at ~/Library/Preferences/com.rsa.Software Token\Desktop.plist) and manually updating its two properties: LastXPosition and LastYPosition. Supposedly, .plist files can be edited with any text editor (e.g., TextEdit), but this one seems to be in some binary format; I ended up have to use Xcode's plist editor to be able to make my changes.
Further Pro Tip: Make sure to tab or click out each field that you've edited. If you just type your change in place and save, it will not take.