I owned an In Step trailer when my son was younger, but upgraded to a Chariot Carrier when my second son was born. I loved both trailers, but the Chariot has a better/more comfortable harness for the kids, and seems to be a smoother ride. I love, love, love my bike trailer.
Although, I maaaaay have cursed it's name once or twice the time I got a flat tire and had to change it with two little boys running wildly around.