I just wanted to let you all know about my experience buying a Newertech high-capacity battery for my 15" aluminum G4 powerbook. It is really great. My apple battery was dead after not much more than a year -- just past the warranty, but they were totally unhelpful. (I've had Apple laptops since 1994 and the batteries never wore out like that before). Anyhow, I'm over my bitterness with Apple b/c I will never buy one of their batteries again. It took several charges, but the Newertech battery is amazing. According to Coconut Battery it has 5107 mAh, compared to Apple's 4400, and it lasted for more than four hours of regular use yesterday. I'm posting this for two reasons: - one, b/c when I was looking I couldn't find anyone confirming that this battery works so well, even though it was generally recommended. - two, b/c if you've purchased this battery, stick it in and see that it does not live up to spec, you need to calibrate it several times. This is a pain in the neck, but so so worth it to get all the time. I think I had to calibrate it (run from full to sleep on battery alone) five times, and each time it showed more of a capacity, till it stuck at 5107 mAh, which is more than the 5000 promised. So far I am a happy customer.