I have an iPad 2 and I have noticed how slow the charging is via usb through my early 2009 iMac. I have read where usb only outputs around 5-6 watts and the charger provides 10 watts. Would charging through usb from the computer be better for the battery, since it is charging slower? By the way this is my first iPad and it is pretty amazing. Definitely worth having even for the naysayers that have and iPhone 4 (as do I).