I have the same problem (battery model A1189) with my Macbook Pro 17" (approx. 2 years old) - the mac started shutting down randomly when being used without the power plug, and then, today, the track-pad stopped working. I had previously read about the battery problem so I quickly figured out what was wrong. However, one thing I didn't know is that the casing could MELT! That's right, and I don't mean the battery casing, but the casing of the MBP!
You know where you push to open your MBP? Well, on the far left hand side, I noticed that the whole top frame had shifted ever so slightly. I tried pushing it back in place and made a DENT in the machine! There's a frickin DENT in the machine made by my finger!
I'm taking this to the Apple store to see what they have to say about it, I hope they can fix the dent as well as give me a new battery!
I just started having the same problem the last couple of days. The battery is starting to bulge, the trackpad button is no longer responding as it used to. Defective products should be replaced regardless of the warranty. The battery did not stop holding a charge because of use. It is falling apart. I don't have a mac store nearby, it will require a four hour car ride to visit a store. Needless to say, my first mac may be my last mac.