We're just slightly post-newbie with about 7000 tandem miles under our belts. No wind, on the flat you can't help but be faster unless there is really an unusual difference in cadence. Serious climbs are hard work whether on a single or tandem, but it's harder on the tandem in our experience since you don't have as much flexibility in position and cadence as you do on a single. A serious climb would be 2000+ feet in 10 miles. Rollers are what can really kill the captain on a long ride. It's easy to skip that last downshift as you might on a single and grunt out the last couple of hundred feet, but the stoker, even a strong rider, may not be putting in that extra effort; this can wear the captain out very quickly. A kissing cousin killer is a sudden uptick that leaves the team in too high a gear with both captain and stoker expending a lot of effort.

Anyway, it all gets better; you're never alone; and the downhills are something special.