Garmin Edge 305 users...

[Mr. Bloom]

Can you really map out a course before riding, down/upload it to your Garmin and then ride the route? I think I remember someone commenting that they could set some kind of alarm to tell you if you'd gone more than 25ft off course.. something like that.

I've not spent anytime figuring it out, but it's my understanding that it works as you described. I'm hoping to have time this summer to figure it out.

I might suggest you look at the owner's manual on Garmin's site.

Notwithstanding this, I LOVE, LOVE, LOVE my Garmin!

[7rider]

A quick review of my owner's manual, which I keep handy on the computer desk:
I can't find anything about "loading" or "uploading" pre-marked routes in my owners manual. You can ride a route, and mark spots along the way. Later, you can go back and navigate straight lines between them. It seems horribly labor intensive -- a slow and ponderous process (especially naming the points so they make sense!).
You can create and edit "courses" - again, based on a previously recorded ride. You need to use the Training Center software that came with the unit for that.
I think (although I'm not sure) you may have more functionality using an aftermarket program like MotionBased to upload totally new courses (assuming someone else rode them and shares them). I've uploaded routes to Bikely.com via motionbased (requires some file coversions) so perhaps that route can go in the other way, too.