My wife and I did a tour last summer about 820kms on a Santana Arriva pulling a BOB trailer and using rear panniers. It worked very well for us. We bought it as a demo in Calgary for $4000.00 CND. You can go to http://www.santanainc.com/thebikes.html to get an idea of what it is set up like. However there are many bikes out there that will work great for touring.
As far as hills go it is generally harder to climb on a tandem but the newer tandems are definately easier to ride than your 3 speed.
As a team you start ot work together fairly quickly or you die on the road one of the two.

Have fun