Charges (although more slowly) on both my 13" unibody MacBook and my PC
The USB charging problem comes from the iPad requiring 1000ma to charge.
USB ports normally only supply 500ma, the wall adapter is 10watts or 2000ma @ 5v (standard USB voltage)
I never knew it took 4 hours, but that makes cents. Q.Q
I just use it all day and put it on the dock at night flashing pictures, and its fully charged in the morning. The more I read these boards the less geeky I feel.