I recently had an experience with the company Powerbookmedic.com that I wanted to make you aware of.

I ordered a battery from them for my powerbook. The battery came and would not work in my computer. It appeared as if they purchase the batteries from Apple and add a metal plate themselves. In addition to the plate being jagged and bent it appeared warped as my computer would only recognize it if I applied constant physical pressure. I called their support and the kindly indicated they would replace it if I sent it back, but I had to pay to send it back! After a lengthy discussion in which I pointed out that I had already paid to ship the battery once they agreed to provide me with a FedEx label. When they finally reimbursed me for the purchase, they claimed it was not their policy to refund the cost of shipping to a customer even if that customer never actually received a working product. In the end I wasted a couple of weeks and $8 to get nothing in return from Powerbookmedic.com.

Be warned of the type of service you are likely to get by trying to save a few dollars and buy your mac supplies from this company.