Which Battery to Buy?

I'm the market for a Powerbook 12" battery - whichever can give me the most capacity. The Apple Canada store sells it for a ridiculous $160. I've searched on eBay and come up with a bunch of results, which can be accessed here. There are batteries as low as $30!

Any recommendations on which battery? What's the difference between the different mAH types? Some are 5200 while others are 4400. How do I know if one third party battery will give me more running time than another... is it based on mAH? Will these batteries be significantly inferior to Apple's? Apple's battery has fairly bad reviews.

Thanks!

That looks like a fantastic battery! Unfortunately it costs about one third of the computer's value. I suppose it would be a waste to buy a $30 one, though.