I used it for the first time a few days ago and it did great - I rolled over gravel, asphalt, a metal dock, then a slippery wood dock - no problems. I didn't secure it to my kayak very well at first and it rolled into the river - it does float at least long enough for me to reach in and grab it. I looked for other carts that received good reviews, looked durable, and were made in North America and was hard-pressed to find something that fit all these criteria
Anyway,I tried using the provided strap to load the boat. It was a real struggle. There is no foot to hold the cart steady, so it tends to roll away on you. Keeping the boat on the cart with the strap seemed near impossible. Finally, I found that if I added a bungee, and then used the strap afterwards (I personally don't think the strap is doing much) and bungee the cart to the boat while holding the rear of the boat just so, it works.
Now, we start to roll it around. Going straight, it works okay on asphalt, a concrete boat ramp, and a boardwalk. The cart came loose on a turn, and again going up a small curb drop. I sent a complaint to Paddleboy, but they didn't seem much interested in satisfying a disillusioned customer.
At about $25, the Molly would be a good value, and with some design changes and better wheels, it might be a good product. In case the manufacturer reads, this post, I would have certainly appreciated a satisfaction guarantee on this purchase. There was no defects, just a design that doesn't work.