I got the last good macbook--the first 13-inch unibody, with a trivially replaceable battery and hard drive. Wish Apple would've kept that design around, it's fantastic.
I have the same laptop and replaced the battery last year and also upgraded to a SSD. This made my old 2ghz C2D just as fast in everyday tasks at the i5 air I got from work.
in other news I just ordered a new MBP Retina to replace it :)