Having sought advice on trail-a-bikes on this site, and been grateful for having received it, I thought I'd offer some experience. For a year my 5- and then 6-year-old daughter rode an Adams attached to my hybrid. It worked well and she enjoyed it until about a month ago when I started to notice some play and wobbling in the hitch. In researching a replacement for the hitch, I came across some posts about the superior design of the Burley Piccolo. I purchased the Piccolo and the posts were right. It is much better: the seat and the handlebars adjust more easily to a better position (at least for my daughter); the six gears permit the child to pedal even up a hill when a single-gear trailer would leave her feeling useless as a ride participant; and most importantly, the unit's attachment to a rack rather than the seatpost virtually eliminates instability when the child shifts her weight and allows the trailer bike to follow more closely behind the adult's bike, making turning easier. The only negative is that the Burley (inexplicably) does not run the frame down below the front ring as protection, which means that if you rest the trailer unattached on the ground you risk bending the ring and breaking off the rubber guard (which is, also inexplicably, riveted to the ring and thus can't be replaced without replacing the ring (and perhaps the crank with it). The advantages well outweigh the sole negative and justify the price difference for anyone who can even remotely afford it.