I tried rendering into my Garmin Nuvi this weekend and discovered a number of inconsistencies in north Georgia (where I'll hopefully be commuting soon).

I grabbed my handheld unit for geocaching (Garmin GPSmap 60Csx) and recorded a trace at 5 second intervals from my subdivision down the secondary roads to Ringgold, then back up I-75 to E. Brainerd.

Not sure how well a job I did in Potlatch, but I've set the trace to public if anyone wants to work on I-75 for a few exits.