I noticed a few more things about charging the iPad:
- charges with my MBP
- only charges when I plug it in first, if I plug in my iPhone first, my iPad doesn't charge!
- didn't charge when I plugged it into a HP desktop
- some Apple computers and displays can supply up to 1100 mA (the normal is 500 mA)
- but they only supply this much to the first device that requests it