MacBook battery replacement

I'm looking for a non-Apple (to save $) MacBook battery replacement. I've so far found only http://store.fastmac.com/product_info.php?cPath=10_4&products_id=151 from FastMac. I don't know anything about them, and they're $99 instead of the $129 that Apple is currently asking, so I'm not sure if slightly smaller price makes up the uncertainty of buying this product. Does anyone have any advice or other recommendations? Thanks