We are running a Shimamo 10 speed on our tandem. While I must say that I got a little lazy and did not change it in time recently, and it cost me a middle chainring in process, I don't find the 10 speed to be less reliable or measurably less durable than a nine speed.

We ride long distances and tend to go through stuff more often than most people so we have opted to go with a single speed chain for the timing chain. Since the timing chain is a single speed, it makes sense to me to use a single speed chain. The fact that I can pick one up for less than $15.00 makes good financial sense to me too. I don't seem to be able to notice the weight differential.

Since switching to the 10 speed we have completed two brevet series (200, 300, 400 & 600 kilometers) plus training as well as keeping our R-12 alive for almost two years (on the ten speed). We have not broken anything - yet... We are working on another series and have a 400k coming up next Friday, I let you know if we have any trouble. By the way, we are not by any stretch a lightweight team.

Your results may vary.