Yeah, but they don't make Di2 for triples (yet). Otherwise I'd be tempted to get it for my tandem.

What I found on my last double century (Knoxville), though, is that I bog down completely on a 15-18% grade at 5 kmh on my 44x17 fixed gear. So when I get off the bike and start walking, I find I'm doing 4 to 5 kmh anyway. Always wondered why anyone would use a triple to ride at slower than walking speed; I guess you can spin up the tiny gear and still maintain a reasonable (faster than walking) speed on the steepest climbs.

Luis