I passed the Blackbook to my husband... if he wouldn't have needed a notebook, I would have just kept it. It works beautifully, but I am loving the Alum as well. And I do love the weight difference. That's what's so enticing about the Air. But back to the XBench thing, I really don't know much about what it's testing, I need to read up on it to understand it better.
IMHO, the test is slightly flawed because it presents an average of all the scores to come up with the final number. If you are doing graphic intesive work than your score almost triples. On my 1.6/80gb using the whole test, it gave me a 42. When I run it on without the graphics test, it throws it up to 103. Yes I know that the graphics card is better but I have never had a slowdown on watching streaming video or graphics processing.
I don't know what to take from it, but I can tell you for normal office work and occasional photoshop and music stuff, it's pretty fast.