BTW – Garmin's 605 or 205 are fine for naviagating…you've just got to use a course (.CRS
Really? I'm getting really frustrated with my 605. All I want to do is follow a tracklog of a previous ride – whether one of mine or someone elses. That's something a basic etrex could do 5+ years ago – a little arrow pointing in the direction you needed to go in.
Courses don't tell you which way to turn – they tell you when you're 'off course' (frequently, particularly offroad under trees where there may be inaccuracy in either the original or current location, and uselessly as they don't tell you which way you need to go to get back on the course). If you're course is a lap of, say, Richmond Park this might work OK but in the woods with tight knit singletrack that might cross over itself (eg a figure of 8 loop) it's useless.
The "navigation" option doesn't seem to work at all – just connects a load of random points offroad.
Following a tracklog "as a line on the map" again is OK as long as it's always obvious which way is 'ahead' – go to navigate a loop off the main track and it gives you no indication whether you should be going clockwise or anticlockwise (so you potentially end up climbing up the descent).
Oh, and navigating a course resets the timer/distance etc so you lose your total ride distance if you did any riding before you arrive at the start of the course.