The mbp 13 is a fine machine itself! Plus you can perform upgrades on the pro. Not so on the Air. It is what it is. Puppy's all sealed up and soldered together. Not a bad thing if you know what you want out of your machine ahead of time. ( I read that you upgraded your hd to a solid state- that should scream past the fastest Air available, with it's 2.4 processor and 4GB RAM. The graphics card in the pro is a bit faster too if I am not mistaken, and you've got FireWire connectivity in case you need to transfer data fast. A fine computer for sure.
On the Air's battery life, the 11.6"er is rated for about half that of the 13" pro; 5 vs 10 hrs, ( the 13" air is rated for 7 hr battery life). There are external portable
battery packs that plug into the macs magafe port to add up to 15 more hours of battery life for those in between charging sources for longer periods of time. Also plugs into iPads. Bonus! 8) $169
There's also the airline/auto/USB combo charger by itself, made by Kensington for $69. Can charge the iPad, MacBook, and whatever else that charges via USB on the go. Apple makes a auto/airline charger, minus the USB charging ports, for $49.
Back on topic regarding the iPad as a laptop replacement, I have been considering getting a Clamcase for the pad since first seeing it. If I end up not going the Mac/iPad combo packed into a single
bookbook route, I'll probably get the
Clamcase. As long as i can pop it out as needed, it appears to be a nice accessory for the iPad user looking for a more laptop-like experience.