MBP13(2009)->MBP13(2010) for me was 'meh'.
Battery life: I personally noticed that off the bat, the 2010 needed a calibration. The 2009 was perfect out of the box. I honestly feel that I am not getting 3 hours more, but more like .5 to 1 hour more.
Processor: Nope, no noticeable difference (its .14GHz).
GPU: I haven't noticed much here despite the 80% increase. I don't really do anything graphically intensive, just youtube and maybe some flash games/sites.
Inertia Scrolling: At first I didn't care, but with long webpages/documents this comes in handy as you can 'build speed'.
Aluminum Finish: This has definitely changed. The lid of the new MBP13s is grainy, whereas the 2009s was 'brushed' horizontally.
mDP: The added audio feature is nice, but there is much confusion over which cables work. I personally stick to my audio+mDP -> HDMI cable from monoprice which still has a usb+mDP cable.