When we first started using the Nuvi's we wasted a lot of gas chasing back and forth in areas and not paying close enough attention as to the "driving distance" and time estimated to the next cache. For example, if you're caching on the Bailey's Island penisula, Route 24, the Nuvi might tell you the next closest cache is 1.7 miles but that cache may be on the South Harpswell Penisula, Route 123 and require 20 miles of driving! On the newer Nuvi's the distance to cache and driving miles are displayed as soon as you call up a cache just to the left of the "more" button. Paying attention to this will save you gas and time.
Also watch the directional arrows if you display a bunch of caches on the screen. The power trail caches will give you a good example. Sometimes going to the caches closest to you as the crow flies will result in going back and forth.
Lastly, there probably could be a whole thread just dedicated to caches that a Nuvi just won't get you to, like any cache located right next to the Interstate. Last weekend we did Wallamatogus Cache, GC1ZRGN on the Castine Penisula, one we've called a top 10 fovorite for us. The Nuvi would never get you anywhere near the starting point. (Should you do this one and you should because of the scenic vistas from the top) then use Parmacheenee's details as to how to get to a good starting point.
Like other tools, the Nuvi is very useful as is the export macro, but it's by no means perfect. Sometimes using the topo map when viewing the map of the cache on GC.com will show you a trail or best way to access a cache.
Anybody know how to delete a single cache from the Nuvi after you've found it?
Sometimes the road less traveled is less traveled for a reason.