We test rode one recently, it was a 700 JointVenture. We own a Co-Motion Periscope Torpedo. A few points:

• My stoker said she couldn't feel my rhythm, thus couldn't predict what my movements were. She didn't feel very confident.
• I thought it was not as stiff as our Periscope, but was just as compliant.
• It's got SERIOUSLY LOW gearing.
• The front derailleur takes some getting used to because it's not indexed, and there are 4 'chainrings.'
• Contrary to popular belief, there is no gear reduction between the two riders, thus if one person is not pedaling at the cadence of the other, one of them is not producing any power to the wheel.