did a ride on the Williamsburg Parkway (closed to auto traffic for the ride) on our Burley duet,with our daughter on a trail a bike, and pulling our friend's child in a Burley trailer.
Worked fine, but turning it around took some space.
I'll admit that jumping in a pace line at 24mph with this rig may not have been the brightest thing I've ever done.
Seriously, it works fine mechanically. Given the room it takes to turn it though, and the time to accelerate (such as through an intersection) I would only do it for casual riding in a bike friendly enviroment, such as around the neighborhood.