In the age of affordable cloud storage and server builds, i no longer need a 750GB hard drive in my laptop. Just give me an internet connection either via free wifi or tethering to my iPhone and I can access all of my information including movies. Keeping it centrally located also eliminates the need to sync revisions, etc.
1) Crash Plan for off-site backups of my primary computer (and separated file access from backup sets via the app on my iPhone and iPad)
2) Pogoplug - live media server for WD TV Live and remote movie streaming via app on my iPhone and iPad
3) Windows Home Server (WHS 2011) for client computer backups and on-site redundant storage and backup of everything
With that said, the Macbook Air would be my perfect machine. I just have not been able to convince myself to purchase it as I would need to get the $1,500 model. I am on-the-go constantly and not having to worry about being close to an outlet is relieving. I was in the Apple store the other day and while on paper the Macbook Pro 13" is not "that" much heavier than the Macbook Air 13", you can certainly feel the difference and I would feel the difference considerably hauling my bag around from site to site. The Macbook Air is so thin and light, and the battery life so fantastic that I could just slide it into the internal side pocket of my bag (not even the laptop compartment) and I wouldn't even know it's there since I wouldn't need to bring the power cord.
I use handbrake 4-6 times a week, and I know the Macbook Air isn't ideal for that. However my current Acer laptop with an intel i3-2310m isn't ideal either, yet it encodes a 720p mp4 movie in about an hour. I'm perfectly content with that performance, and I'm sure the Macbook Air would do better than that since I would be getting the i7 model.
Once Ivy Bridge comes out to the Macbook Air line, I will swoop in and buy an i7 Sandy Bridge Macbook Air refurb like I did with the iPad 2 16GB wifi refurb when the "new" iPad came out