We had some problems with the chainsets, we used standard TA rings, which needed reinforsement on the back centrally spaced tripple. The inner ring having wound up the first time we tried it out. Unfortunately we hadn't locked the bolts in and we spent at least an hour on the first day in the mountains, finding all the bits to put it together again. Also, while we managed to build up the wheels with 13 gauge spokes, so had no problems there, the back rim eventually cracked at the weld and we had to rebuild the wheel with a new rim along the way. Otherwise we had no problems keeping up a good 100 miles a day average.
I still have the tandem hanging in the halway but don't get the chance to use it unfortunately as nobody trusts me to throw them down hill sides like my younger brother did then!