Grad Student IT guy
My $.02
I've had experience with a few 15" Apple laptops before I purchased my 2011 MBA i7.
2004 15" Powerbook 1.5
2007 15" Core Duo Macbook Pro
2009 15" Core 2 Duo Macbook Pro
I decided to try the 13" Air in 2011 because it's performance has gotten a lot closer to the Pro - my last pro had 2.66 Core 2 Duo and the 9600GT dedicated GPU.
Size/weight:
It's literally 1/2 the weight and I schlep my laptop everywhere for work and for school, and I like it. I didn't think it would make a difference, but it has - It weighs as much as school book and fits better in my briefcase.
I liked the larger screen 15" as it made it easier to edit movies, photos, and game. The upside is that the 15" didn't fit on the tray in economy on planes, the train, and forget about the bolt bus. The MBA does that well.
Performance: I used the 9600M GT in games so I am taking a penalty with the integrated GPU - but it's not super noticeable - I'm lvl 57 in Skyrim and play Civ 5 (in bootcamp). The CPU is considerably faster than my old system and the SSD combined make it feel faster overall. I handbrake movies in 1/2 the time. OSX and Bootcamp load really quickly - if you get the MBP get the SSD - you'll love it.
Photoshop, iMovie all work well - Screen real-estate is the only hit for me - You can get a second monitor if you really need it.
Overall MBA over MBP:
Weight and portablity (fits on tray in airplanes, trains, buses, weighs nothing).
SSD makes it blazing fast - Skyrim loads much faster than my friend's gaming rig.
My MBA doesn't creak like my previous MBP (unibody) did.
My MBP 15" roasted my thighs - the MBA is cool as a cucumber...
MBP over MBA:
15" screen - I miss it for photo editing and iMovie.
Dedicated GPU (the 330M GT) is considerably faster if you really need it for apps. Compared to my 9600M GT (the older GPU) it's fast enough.
Screen on my MBP was easier to clean.
end of my $.02 😀