My macbook pro battery died much sooner than the mac should have. Replacing it would have cost me $230, through iFixIt - much, much less.
The installation was easier than even I expected.
Not perfect, though. The buttery should have a softer part that allows the trackpad to "click". Well, it's there, and the trackpad "Click"s, but it isn't soft enough (or deep enough) and the trackpad doesn't "click all the way through". A bit annoying.