I never had any luck using the .gpx routes. My 705 would just shortcut direct from the start to the finish--useless.
So I have been using .tcx Courses, and use the Training menu of the 705 to run them. They load instantly, and never try to recalculate a route. The route shows as a purple line on the map. But, there's normally no warning of an upcoming turn when viewing the map. That's usually not a problem. (It does have a list of upcoming turns on a separate screen, with times and distances updated on the fly)
But recently, I tried the ridewithgps.com .gpx cuesheet only file. It worked great. Even though it only contains the turns, it loads quickly and accurately, shows the same purple route line, and gives me street named warnings 30 seconds before each turn.
(I did seem to miss one turn's prompts last time, even though the purple line was correct. I'll have to try more routes to see if there are any more problems. And I always load the .tcx route as a backup option)
select this one from the downloads section when a route is displayed:
GPX Route (.gpx)
Only the cuesheet entries, not the entire track. Useful for the Garmin Edge 205, 305 and Edge 500 for turn notifications (turn by turn directions)
ridewithgps is my favorite route creating site. It shows the distance and elevation graph as I create the route, and it's really easy to back out a section and try a different route. I tried bikeroutetoaster, but it's really hard to correct mistakes--I often had to start over from the beginning.