Read the reviews. Turn-by-turn does not work as expected. I don't have an Edge, so I can't comment on that model.

I chose mine for the AA batteries - as I use it for touring. When my planned route didn't exist, I was able to use turn-by-turn to get me around it. I haven't reliably found a way to pre-plan a route and get turn-by-turn directions for that route.

Don't blame JUST Garmin. I don't think anybody has this down yet.