I ran one for close to 3 years delivering and picking up shipping containers. Company I used to work for had two of the 48' Landoul's and they rented the containers. I would pull out to unload and winch them back on. Even did two 20'ers, chained them together to remove them from container or load. We loaded at the yard with a packer or large forklift.
I have had the KW tractor get stuck in mud/sand and used the sliding tandem to push the tractor out. Or had trailer get stuck and just lifted trailer and repositioned tandem on solid ground and pulled on out.
Another good thing is if you move tandem all the way forward it is like backing a 20' trailer. Except for having to watch out for the wide swing you can really get into and out of tight spots.
They are VERY expensive! When the company bought the second one they bought it used and I had to replace the complete deck. I replaced the wood with flat steel and gave it a complete paint job.