A lot of it is simply backlash toward people who've started acting as if the MB/Ps are Terribly Heavy Laptops that were Impossible To Bear before the Macbook Air came along.
All this tells me is that you really don't travel very much.
I can't count the number of threads where people have started recommending MBAs to high schoolers looking for all-in-one college laptops under the pretext that "business professionals don't need optical drives". As long as MBA fanboys keep treating the MBA as the second coming, plenty of people will be only too happy to pull them back into cold, hard, reality.
Oh, I have my reservations about the performance trade-offs with the MBA. But then again, I'm upgrading from a 7 year old Graphite iMac - the MBA should be plenty fast. But I am not really sure what FireWire is used for, so I'm probably not as computer-studly as you are. But half the weight and volume of the MBP are pretty compelling to someone that travels 16-20 days a month. I think I'll wait to get my hands on one at the Apple store ... hear the first buyer reports ... and see the SSD benchmarks. But it I find it lacking, I'll probably just buy a new desktop computer.