Is it safe to buy MacBook Pro batteries on eBay? My 15" MacBook Pro 5.1 (late 2008) battery is inflating to the point of nearly breaking the unibody battery cover, so I'm really into replacing it as soon as possible. There are loads of these batteries on eBay (mostly UK sellers with high reputation) that cost less than half of the price I'd have to pay for a battery on a local Apple reseller store.

My question is: is it safe to purchase batteries for MacBook Pros on eBay? Are there any known issues or ripoffs that I should know of?
Another option for longer term (after you have determined why the battery is expanding like it is) may be to see about getting one of the Newer Tech (or other known manufacturer) batteries for your MBP, as they have longer life ratings for the charge. Newer Tech is available from Other World Computing (www.macsales.com), and I've seen it from a few other online sites as well. (I do not work for OWC, but have been very pleased with their products and service) The NewerTech ones I've checked on are rated at higher mA ratings than the original Apple batteries.