I went with the MBA. For me, MBP doesn't offer much over the Air.
The CPU is only barely better and in my usage the difference in negligible. If 13" MBP had i3 or i5, then I might think twice but since it's the same old C2D, MBA was no brainer in this category.
The GPU is the same in both machines. Although I bet MBA's is underclocked, I don't really care. I'm not planning to play games as I have PS3 for that so 320M is more than fine for me.
RAM wise MBP would have been better as it can take up to 8GB and it's user-upgradeable. I ordered my MBA with 4GB and I doubt I'm going to need more than that. If Apple offered no option for 4GB, then I would again think twice because that doesn't sound too good when I think about the future.
SSD vs HD is one the biggest reasons why I went with MBA. I know I can get MBP and upgrade its HD to SSD but that's an extra expense and brings MBP very close to MBA in terms of price. MBA's SSD may not be the best one on the market but I'm sure it will be lightyears ahead of any HD. I'm also fine with 128GB as I just ordered a 500GB 2.5" external HD for 40 and I already got one 250GB which is portable (+ 2x1TB and 500GB that are not portable). I will keep most of my data in my iMac and externals, only some photos and music goes to the MBA (I got the external for videos so I can take it with me when I go for a longer trip).
MBA's hi res screen was also a deal-breaker. I don't know is there a difference in quality but according to AnandTech, the screen is very good and the extra pixels are just making it even sweeter. Again, if 13" MBP had had similar screen, the decision might have been harder but since it does not, MBA is the winner in this category.
Battery life is inferior in MBA but in all honesty, how many of us
really need the 10-hour battery life? Of course it's something that is nice to have but not something that at least I would need. 7 hours is exactly what I hoped from the new MBA and AT's review and user comments show that you can get up to 10 hours off of it with basic usage. That's very, very nice from an ultraportable.
Multitouch trackpad and second USB port just sweetens the deal and makes it more similar to 13" MBP.
I don't think I really
need the extra portability what MBA offers but due to the great updates what MBA got, I find it to be much better deal overall than the 13" MBP. MBA is about 700 grams lighter and little bit smaller form factor but with the same sized screen.
I don't know yet how much I'm going to carry it around but IMO extra portability is never a minus, especially when you don't compromise on the screen size or other specs. Due to the portability, the weight or size won't be a reason why I can't carry it around.
I have a 24" iMac as my current main machine (possibly secondary soon?

) so if I need more power or storage, I can always use my iMac. I'm sure MBA will be a perfect secondary computer for me and I can't see why it wouldn't work as a main computer. Some things make MBP better, like more storage and upgradeability but if those things don't bother you or you find the advantages of the MBA to be greater than its disadvantages, it's an amazing machine.
Of course, MBP update may change the game but personally, I don't like the waiting game too much, especially when I know that I don't need the extra power. I tried my luck with iMac waiting game and all I got was a marginally better GPU. Besides, MBP would still be bigger than the MBA.
W000t my MBA just prepared for shipment!
I didn't know they ship on weekends but I'm very happy that they do