We used one for several years. Got it used for $100, fixed it up
with a few things and sold it for the same price.

I recommend getting one with a cloth sling type seat, rather than a
solid plastic seat as I think the cloth seat is more comfortable.
Also make sure you get wheels with rubber tires. The larger the
wheel, the better ride it will have.

Kids will often go to sleep in a trailer, so get one that is easy for
them to do that in, ie, something they can lean against when they
fall asleep. The trailer should have a good harness system for the
kid as well.

Also make sure they allow for variable ventilation, depending on the
weather. We found our daughter would not go to sleep if there was a
breeze in the trailer, button it up, and she was out in a minute. A
good trailer should have a solid front wind screen to keep water from
coming off your wheel out of the trailer if you get caught in the
rain.

Kids love to toss stuff from the trailer. Make sure the trailer is
toy tight so that you don't leave a trail of tot toys.

I think all trailers are about the same given the above. More
expensive trailers will be lighter and easier to set up. Ours was
steel and weighted a ton, but it worked. The biggest problem with
trailers is they are large wind brakes, so weight is not as big an
issue as you might imagine.

Bruce