Those trailers really make it easy. The bearings do a lot of the work for you, plus the big wheels help a lot. When I made a cart for my dog with one, I could put two 30lb kids in it, and the dog didn't feel a thing. Well, maybe she felt it, but it definitely didn't slow her down.
I have considered taking one of those trailers on a trail. I know a few trails that are just wide enough, and it would help me out when taking all the kids. Haven't done it yet though.
I've taken a vow of poverty. To annoy me, send money.