Mine has been powered from the Powerlet socket for the past year with no issues whatsoever. Just make sure you buy one of these (scroll down
http://www.powerletproducts.com/prod...wer_cables.php ). I do not use the audio features while riding so I have not encountered any static issues to be concerned with.
As a pure power provider the powerlet connection is solid and easily enough to unplug at rest areas.
Keep in mind that if you leave the bike long enough to worry about bike battery discharge than you will want to take the GPS with you. When the Zumo is "powered off" while still plugged into the bike there is very little battery draw on the bikes system. You should easily be able to leave the GPS connected to the bikes system overnight without worying about killing the bikes battery. But again, if left on this long, you should disconnect the GPS from the mount. The mount with no GPS inserted does not draw any power from the bikes battery.