I actually had a 15" in my cart, ready to go, until the end of the keynote. My justification is I think I can live with the 9400M, especially with 4GB RAM, better screen, FireWire (have a few drives that have been using USB instead), and the SD card built-in means no reader attached.
I have an external monitor, so I rarely ever use my current Air alone. When I traveled, it worked just fine (I wasn't editing videos or anything).
So yes, I bought a 13" instead. It's going to be great.