For the pedals, we run A520s on the rear and dual-sided SPD pedals on the front to make clipping in after re-starts a cinch for the captain, and easy walking for us both when off the bike.

We have a steel Co-Motion Speedster, and my stoker is not happy without her ThudBuster - she's fine riding a fully-rigid cyclocross bike on light trails and dirt roads, but on the back of the tandem she wants a bit of cushioning from the bumps that she doesn't see and that I don't call out in time. We're planning to try Specialized's new Cobl Gobl'R seatpost when it is available (carbon post with a funky shape and an elastomer in the middle) to lose a couple hundred grams compared to the Thudbuster, but apparently production is a bit slow and they aren't going to be available for several more months (according to the local Specialized rep').