We have a very small kitchen that did not have room for an undercounter dishwasher. We used a ridiculous countertop dishwasher (an Equator brand, I wholeheartedly DO NOT recommend) for 3 years before seeing this product.
First: difficult to install. We're average DIY'ers with an older house. Perhaps would be easy in a new install, but the template for the countertop is very precise and the unit itself incredibly awkwardly balanced/shaped for multiple fits, etc. And because it's not really an appliance and not really a sink, we couldn't find a plumber or appliance person tat would install it. However, we did successfully get it in. I would suggest you download the PDF of the installation and read it carefully before ordering. It's available on KitchenAid's website. Note the need for your discharge to be "x" number of inches below the lowest point of the dishwasher, it's affected our use.
Now, for the the performance. Size: we did lose part of the storage below one side of the old double sink, but it still allows for some storage. The sink side is incredibly deep, great for handwashing big pots, etc, though if you'd like to do a sink full of dishes, seems like you've got to waste a lot of water.
The dishwasher performance itself: Good to average. Far superior to any countertop dishwasher we've been able to try. I'd say it's close to that of most average (though not higher end with food grinders, etc.) dishwashers. We never screw down the drain and use that side for a sink as well. The racks that come with it are too awkward to put anywhere else. The drain itself contains a fine mesh filter that is difficult to clean, and without regular maintenance, the cleaning performance suffers. It is rather cheap plastic, so I'm hoping there is a replacement part, though I haven't found it yet. The other drawbacks: you really have to firmly push down after pushing start to get it to start, the soap dispenser cup (powder only) and rinse-aid fill spout are awkwardly placed and difficult to fill, sometimes, depending on load distribution, the soap is not completely distributed.
Very acceptable alternative when an undercounter dishwasher is not an option, but given the price, the performance will never be worth it for other applications. However, in comparison to those countertop dishwashers, it was the perfect solution for us.