Okey dokey - found an interesting comparo of several portable nav systems. If you're not ordering nav with the car you may eventually want a portable nav. Here's an article on the routing algorithms:
http://www.gpsmagazine.com/2007/06/g...est_routes.php
When I said earlier that I wanted a nav that did routes, what I didn't clarify was that I want a nav that can take a set of destinations (multiple stops) and build a single route from that list. The BMW system does not do that, IIRC. So far as I know only the Garmin nuvi 770 dos that. But would love to hear otherwise (more choices is always better! ; -).