Disclaimer: I just upgraded from my second generation Core Duo 2.0 Ghz Macbook with 3GB RAM 160GB HDD to a base model 13.3" Macbook Pro.
I paid a bunch of money for it, and will offset that cost a little bit by selling my old Macbook to a neighbor for about half of what I paid for this MBP.
Having said that, I must say that I'm very glad I did this because
a) The display is brilliant. It's even better than my 22" external and before it was the other way around.
b) Despite not being able to get my wireless keyboard working (probably due to dodgy batteries which I am charging as I type this) the keyboard on the MBP seems to be improved. I disliked using the built-in keyboard on my old Mac, but this one seems to be okay to yeah okay.
c) New trackpad. I don't usually use the trackpad, but this one is pretty brilliant.
d) it's thinner. And it seems a tad sturdier without the creaks the plastic one had. I didn't have a problem with that really, but this small thing makes a large difference.
Yes, the keys are in different places, I'm looking at the same 1280x800 resolution, it's pretty much the same machine with a few more MHz on the CPU and a GB less of RAM (which I will take care of later) but these little things add up. I can crank the RAM up to 8GB, put in a big-honking HDD internally, and my external stuff still works just fine with FW 800 to boot.
Plus it's a Macbook Pro now, and believe it or not, that seems to make a difference.
EDIT: forgot to add: Do it.