Installed my Zumo today using the recommendations made in this thread. Thanks to all for providing valuable input. Went with the cig lighter for power and Terry's recommendation to use a Sealink 12v marine type plug. I haven't seen anyone use a switch housing mount, so here are some pics of my install using one made by Leader Motorcycle Products. There are a couple of features I like about this mount, 1) it's chrome, 2) you can easily remove cradle/GPS in entirety for security purposes and 3) adaptors are available to mount cell phone/Blackberry (per photo) or cup holder, etc. using same mount. I highly recommend the product.
I have been comtemplating a Bluetooth earpiece to hear voice commands, something that would be comfortable under a half or 3/4 helmet. I am considering the Motorola Mini H9 which is designed like a hearing aid ear bud, minimal protrusion so it looks like it would not interfere with a helmet or wearing sunglasses with a helmet. However, after riding around today I don't know if I need it. Screen is easy to glance at and read map/directions. School is still out, but has anyone used the Motorola Mini H9 with their GPS?