PB,
No experience with the Shiftmate, but I've read the same threads as yourself and the reports appear positive. As a fallback you could buy the modified SRAM RD from daVinci. We have a Campy/Shimano setup on our 9-spd dV and it works perfectly. I really want to transition to 10-spd either with a Shiftmate or the next-gen modified RD from daVinci, but Todd at dV won't work on this until winter - I believe there is some issue with the lighter-weight chain slapping the stoker's BB since the chainrings are 1/2-sized and the chainring BB is in front of the stoker's BB (for those not dV savvy)