I have a Macbook Pro, 2.16ghz Core Duo, 15"G.
I had to get the battery replace twice because the battery life diminished to the point where I'd get about 5-10min charge within about six months. Luckily, Apple offers extended support for batteries that came with the Core Duo Macbook Pros for up to two years. I've gotten it replaced two times, but the current battery seems to be working well. I'm not sure if there is similar support for the Core 2 Duo Macbook Pros. 28% is pretty low for one year, in my opinion. If you are under warranty see if Apple will replace it for you. Your best bet is to take it to an Apple store if there's one near you.