I just used Edge 830 and its navigation (following routes) functions on a few rides in north Italy and I must say couple of things suck.
1. First and the biggest drawback is the inability to see the route you have to follow. It usually happens at the start/end of the route when the outbound and return route cross. Colors are the same, the arrows showing the direction are to close to each other - it becomes a mess.
2. You can not reverse the route you are on from the device.
3. You cannot edit a route in Garmin Connect app to reverse the route.
4. You can edit a route to reverse it on the web (connect.garmin.com) but..
5. You cannot sync a route with Garmin Connect app during an activity. You have to stop your current activity to sync the new route.
6. When you get off course, sometimes the device will try to get you back on course (for several kilometers) by returning to the point you got off course, rather than recalculating/rerouting to the upcoming parts of the course. The biggest drawback here though is you usually don't know if you are being rerouted to the place you got off course or the course ahead of you. Sometimes you can figure it out by the "remaining distance" if you have it displayed as a field below the map. But at this point you should be pedalling, following the course, enjoying the ride and not trying to figure out what the heck is going on..
Just thought I share my observation here - maybe someone from Garmin is reading this.
