Hi Ben - At present we only have a facility to download routes as GPX Tracks not GPX Routes. However, I'm pleased to say we are adding a GPX Route download facilty as part of our next upgrade, which should hopefully be released in the next couple of weeks.
You shouldn't see any truncation of directions with GPX Track files, as there is no limit to the number if waypoints, but there is with TCX and CRS files due to the limitations of Garmin devices - they can only accept a maximum of 100 coursepoints. To overcome this you can use the Manage Directions feature (in the directions panel on the left of the map) to delete any you don't need or to combine directions together.
I'm using an ancient Garmin eTRex (the first one I think) and although plotaroute is fantastic I'm having two problems:
1) When I download a route it shows up as a track not as a route in the Garmin.
2) If I use autoplot to follow footpaths then the track is truncated when I download, presumably too many waypoints, can I change the granularity so it's less accurate but still good :)