Shelly's other half here. As far as the handling of the tandem goes with panniers and other loading.... I'm not sure if you are wanting a comparison to a single bike or to an unloaded tandem.

First, a comparison to a single. The first thing to realize is that it is long and the second thing to realize is that it is heavy. So nimble is not a word that you would use to describe the riding experience. The tandem wants to keep going in the direction that it is headed, at the speed at which it is already going. (Newton's 2nd law for any former Physics students out there). On the flats and downhill, it is a real joy to ride, stable and smooth. But uphill, unless both of you are strong riders, you will find that you are slower, perhaps considerably slower, on the tandem than either one of you separately.

Compared to an unloaded tandem - it's just like that, only more so. Heavier, less responsive, and harder to pull up the hills.

If the two of you are mismatched in riding ability I can't imagine a better way to share the experience without one or both of you getting frustrated by the differences in speed. Of course, I just may be spoiled because I have a very sweet-tempered stoker.

jeff