My nuvi 650 works just great attached to the rearview mirror. Great reception, fast signal lock, and good accuracy. Frankly, I was (happily) surprised by this.
Here are a couple of shots of my nuvi 650 mount, inspired by landcruisersteve's original post. It's hardwired to the switched power available in the "mystery plug" found under the driver's side a-pillar cover.
Joe
