Well said; I work at Wacom, and I don't think I could have explained it better. :)
Powering the pen does consume some energy, but I believe the panels used for TabletPCs can actually be classified as "Low-Power" USB devices, so the drain isn't nearly as much as, say, the hard drive. I'm not sure how efficient the Windows Ink code is, but our driver, which hasn't taken extreme pains to be performant, peaks at about 3% of a 1GHz CPU when the pen is in range.
Powering the pen does consume some energy, but I believe the panels used for TabletPCs can actually be classified as "Low-Power" USB devices, so the drain isn't nearly as much as, say, the hard drive. I'm not sure how efficient the Windows Ink code is, but our driver, which hasn't taken extreme pains to be performant, peaks at about 3% of a 1GHz CPU when the pen is in range.