My update on Kevin's counter is that I've now measured 14 courses using it, including a couple marathons, a couple half marathons and a smattering of others. It is still running really well despite some nasty conditions like awful road surfaces in DC following winter freezing and thawing, and getting caked up with mud on the Frederick Fairgrounds horse track.
Occasionally as with other counters the gearing at the hub gets a little noisy from time to time and I find some oil quiets things down acceptably. On mine there is a slight ticking sound at the counter end (on the handlebar) that I can't quite figure out. It's slight and I can live with it.
I love having the counter right up close to my aging eyes, and I hope there is a way that a handlebar mount can be made available as an option for more measurers. But I understand there are economic considerations that make it a little tricky to produce on a large scale, especially when offering a choice between 6- and 5- digit counters. Maybe only offer one (I vote for 5 but would understand if the majority goes for 6).