I hated the cart when I tried it in my first playthough, but I just tried it again ther other day due to having to move my entire base a days run across land, and I've been wondering if I remembered it incorrectly, of if they improved it.

For the most part, I'm just pulling it through plains, so it's not as hard as it could be, but some of the travel is through swamp and most of it is on the side of a mountain, so still sloped and rocky. I've had the cart fall apart a couple of times, but I can make the trip in not much longer than it takes to run, and that's with (in the first trip) a significant amount of metal, and (in the latest trip) over half full of rock.