Moorlock,
You two will quickly find that the tandem evens out your abilities and allows both of you to finish a ride at the same degree of exhaustion. We rode our singles for years before discovering tandems, and our rides were always a serious compromise on my part. Mostly, we would plan different routes and hope to meet up near the end and ride a few minutes together. Now our single bikes get pretty ignored!
We ride together so often and it has become so much a part of our lives that we built up a second tandem only a couple of years after buying the first. You'll discover how and where you like to ride, and then kit up your tandem to suit that...no matter what anyone writes, there are few limitations. Our tandem is superlight, but has the gearing for high speed on the flats, as well as climbing grades of over 20 percent. We have even done some lightweight touring on this bike, but in truth our other tandem is better suited to the added baggage. Our front rings are 53-41-28 [with a reserve 54], and our rear cassette is a Sram XX 11-36. The range is enormous, but we use every bit of it since we love the mountains. We had a lot of sorting out to get it all set up, but it has run perfectly since and shifts great.
Enjoy