I've replaced my MBP's battery twice now. No love from Apple regarding free battery replacements, so I did them all myself. Took far longer than it should have, being used to swap batteries on the fly with our Thinkpads, but passable.
The new MBP offerings are pathetic, and unfortunately I've maxed out this mid 2009 MBP as far as it can go and it's still struggling. Probably replacing it with a Thinkpad early next year. :/