I have mixed experiences with my Garmin Nuvi. On one hand, it often comes up with a really brilliant solution that seems daft right up until you magically arrive at your destination by the most brilliant route possible. On the other hand, sometimes it sends me several blocks out of the way for literally no reason whatsoever. It doesn't save me any stop signs or anything. I use it anyway, and mostly just trust it because sometimes it knows something really important like how to avoid an inexplicable one-way street, but I'd like it to put a little more effort into avoiding those pointless cases. And yes, I have traffic, but never has it lit up the map in one of those cases to suggest that it was doing me a favor.
Oh look, I have a 5 minute posting delay. How quaint.