I recently purchased a 15" 2011 MBP a couple days ago. I'm being haunted by visions of the 13" MBA though. Gosh it is freakin slick! I was in Best Buy staring at it again. lol. I keep thinking if I made the right choice, and if I could actually get by on the MBA for the audio work I do. The main reason I didn't get the MBA over the 15" MBP is because there is no way to connect an external drive to record to. (Firewire). USB 2.0 is just not an ideal way to record any type of audio to. My current pc has a core 2 duo and I get by just fine as far as processing speed, so I know that even though the processor is outdated on the MBA, I would still have plenty of power for my needs.
Ideally, when the new MBA comes out, I plan on selling the MBP 15" and getting it instead, since it will more than likely have Thunderbolt, which would allow me to connect to an external drive to record to. I wish so bad that the MBA had a firewire port. I keep going over, and over in my head if there is any way that I could make the MBA work for my needs but I just don't see it happening with this current model. I absolutely love the form factor of it. They say that the MBA could be out for a refresh as soon as June though.
I live in Phoenix, and this is the first time I have wished that Summer would freaking get here already so I can have my MBA!