Well, I've had almost a day now with the Air. It's definitely all that I hoped for.
The only minor issue I can see so far is that the hard disk is definitely noticeably slower, which is to be expected, since it runs at 4200rpm versus my "old" MacBook's 5400rpm.
So, the first time you start any app, it takes a few bounces before it's ready to work. However, once an app is in memory, I certainly don't notice any difference in performance compared to the MacBook.
As I was just saying to my mate Steve via e-mail, that shouldn't cause me much hassle, since generally the starting up of any of my mainstay apps will only occur very occasionally, because 95% of the time, the machine will be in use, or sleeping.
It will only be the odd occasion when a software update requires a reboot that will cause me to have to start them from scratch again.
I'm currently calibrating the battery, so I'll let you know whether the approximately 3.5 hours runtime I got yesterday turns into something slightly better or slightly worse in the long term.
For the time being, at least, I'm a very happy little Vegemite :-).
Now, I'm off to process more than a thousand entries that piled up in Google Reader in the last day, due to my complete neglect of my reading duties! I have a feeling I'll be pressing that "Mark As Read" button towards the end ...