I have the 4 X 8 Harbor Freight. I originally got it because I could fold it up, and deflate the raft in the winter. I ended up building a platform on it, and the extra weight makes it ride much better on bumpy roads, but the platform makes it so I can't easilly break it down and fold it up. I have a 13foot boat. I built sides to box in the deck inside the fenders, and then fixed 2 wide boards like cross bars over the box. The raft rests very nicely on these boards, and there is a "bed" underneath for paddles, etc (although I don't use it much because I drive a truck.
Keep in mind that the HF trailer comes shipped to you as a 200lb package of cross bars, nuts and bolts. It took me several full afternoons to build. Like they say, you get what you pay for. Mine will be an expiriment to see how long a $350 trailer makes it. I don't know if I would take it on a very far trip, like Westwater (last time, I just used the air pump at the put-in), but it works well for my home-based day trip rivers.
The trailer with boat fits snuggly into my "boathouse" (econ sized 1-car garage). With the inflated boat on there, I can rig and run in about the same amount of time as when I kayak. Pretty sweet deal. I think next one will be a sled trailer, if I ever have a big enough place to store it, however.