First post in the tandem section. I have only ridden tandems a couple times.
Once around the parking lot and once on the local hammer-dog ride in San Diego (Cyclo-Vets)
My buddy got a Santana for himself and his GF. 26" with road bars. We decided to take it on a club ride. We were both Cat III racers at the time. Never on a tandem before together and we just KILLED this club ride. I was amazed. We were both going as hard as we usually do, which is to say 100%. But as a couple of tandem novices, we were blown away by how fast we were going compared to the single bikes.
-Z