Thanks for the review. I have the same background as you with many years of Thinkpads, the last year and a half with an X61s. But there were just too many negatives to this 1st generation Air that I decided to wait. I got the X300 and I am very happy. It is a heck of a lot better than the X61s and it's not just the screen.
One thing about the battery, you say you were only getting 2 hours on your X61s with the small battery. I was getting over 4 hours for the first year and down to 3 hours after 18 months. Maybe you just had a bad battery?
It's not loss of features that is keeping me from the Air, but lack of quality in the 1st generation product, ie the problem you had with your first unit. I too don't care about optical drives, however I make heavy use out of USB peripherals so when the 2nd gen Air comes out and fixes that and all the other issues I may make the switch. For now I am quite happy with the X300 and would recommend it to any frequent traveler.