I used the "course" feature of my 305 for the first time yesterday. I had no problem creating the course at MapMyRide and loading it into the unit, but the Virtual Partner feature seemed a bit dodgy.

Every couple of miles I'd get a message that the unit was "updating the virtual partner". Then the vp would suddenly be a half mile ahead of me! This happened about 5 times on a 30-mile ride. And even though I outrode the planned speed of the virtual partner, he beat me by a mile.

Here's what I think happened - I used the "follow roads" feature when I mapped my ride and only mapped points where I though necessary to force it to the route I wanted. When I loaded into the Garmin, I suspect it only "sees" the points I marked. Of course, it can't follow roads, so it assumes a straight line between points, thus giving the virtual partner a distinct advantage.

Does this sound right? I hate to think that a moldering pile of electrons can outride me!

Yeah, I am pretty sure that you're right. The machine figures you are going in a straight line.