We have had our Calfee for one year, with a similar set-up:
Levers: Ultegra 6703
Crankset: DaVinci with FSA 53/39/26 chainrings
FD: Ultegra 6703 with FSA clamp
RD/Cassette: Started with Ultegra 6703 medium cage with IRD 11-32. Switched in February to XT M761 SGS with SRAM 12-36.
Brakes: DA 7900 front and rear
Front shifting has been excellent. Rear shifting was fair with the Ultegra RD and IRD cassette. Switching to the XT M-761 RD and SRAM cassette tremendously improved the rear shifting. Mel at Tandems East recommended the M761 SGS RD over the 9 speed Shadow models. Overall, a noticeable improvement over the Ultegra 9-speed drivetrain that we had on our Co-Motion.
Shifts beautifully, rides beautifully, looks beautiful.