I got an Android tablet last fall to look at using for my dual sport routes. I tried Locus - map were hard to see clearly, but handled tracks well - and OSMand - maps were nice but tracks sucked. Unless they've updated the problem areas in either of those packages, they don't work for me. Also, the tracks/routes that people have change over time - they download new stuff, old stuff gets closed, etc. Just my 2 cents worth.... Oh, and for Nuvi's look at building map overlays... that works pretty good.