I'm facing a similar dilemma as the OP. My first, and last, Mac was a Powerbook 17" 1Ghz, which is almost 5 years old. The battery is dead, and it's running quite slow. I'm a law student, and I've bought a 13" Sony VAIO to take notes due to portability. Right about now, that computer is 2.5 years old. For all of my multimedia needs, I go back to my Mac. Unfortunately, using my old Powerbook with my iPhone has been a pain, especially with the slow USB 1.0.
I've been wanting to buy a new mac since last summer, but I've been waiting patiently for a revision on the MBP line. I've considered the MBs, but I'm not a fan of the plastic. Portability is a consideration, but I don't think that a 15" MBP is "too big."
My use will be much like the OP--word processing, iTunes, web surfing and multimedia. Will I need more horse power than that which a MBA provides if I'm looking to use iPhoto and Handbrake (transferring DVDs to iPhone-optimized mp4s)? I also use Quicken a fair bit, so I may have to install Parallels and Windows XP in order to run the windows version until Intuit releases the new Quicken for Mac. The occasional game (Spore!) isn't out of the question, but I doubt I'd use by laptop for gaming that often.
Any advice would be greatly appreciated. I'm just really confused as to whether I should buy a MBA, a MBP right now, or bear the wait for a new MBP.
You know what I think anyone who considers a Macbook Pro instead should just get one. the Macbook Air just can't be your main machine it's just doesn't have it in it I don't think. Get the Pro!