When the KSG was first announced and there were some tests of it, I watched several videos of it in operation.
As the article you posted mentions, it seemed like everyone had problems getting the gun to operate without a stoppage.
From the reports I read at that time, part of the problems were because the trigger must be released before you pump the slide. That is not the operation with which I am familiar. I fire, rack the slide, release the trigger to reset point, and fire again. It just seem natural to me to use pumping the slide to help bring the muzzle back into position after recoil and to have to change my grip to do that seems counter-intuitive to me. This was on the first prototype guns sent out for review and they may have changed the design since then.
Also, as the article said, short cycling can be a problem.
Both of these problems can be over come with practice, particularly the short cycling.
I do like the design and the functionality of the gun and would be interested if the design was more "traditional" with the trigger release and if the price were much more reasonable.
If you have no experience with a shotgun, you might not find the trigger release procedure to be a problem. Find a 870 and dry cycle it both ways and see which you like...and see if the difference is a deal breaker for you.