I built my cart today and it is already running heavy sheets around my shed, which is certainly better than carrying them by hand.
The build quality of the cart is good and solid. You can forget about using the supplied thin spanner for assembly. Bring your socket set because there are 16 tight bolts to attach the casters, plus 6 bolts for the upright handles. The casters are large diameter and run easily. Two have brakes to stop the cart from running away. The uprights are held in place by bolts running through folded steel brackets, and the joints are loose unless you overtighten the bolts to bend the brackets so there is no clearance between the parts. Slightly loose joints is not a problem, because the uprights still serve their role without losing strength. Insert some washers if you want tight joints. One improvement I will make is to add a rubber mat to the running board
to prevent any movement of the load. For the price, this was a good buy and I recommend it.