Less about performance than capacity
Thank you for all the wonderful scans, Steve--great to see you posting! I LOVE that Sherwood Green set--what a handsome machine!
Bob and I used to joke that a KDS-15 and a DW-IMH made for a harmonious household; the KitchenAid was the "bottom" dishwasher for pots and pans, and the Frigidaire handled all the cups, dishes, and otherwise flat items.
You may remember when the DW-IMH came home--the first load was a bust, and I was perturbed as much by the performance as by the inability to load a plate larger than 9" in diameter. (The top rack hit them.)
But with downsized dishware, good detergent, the true detergent dispenser and double-wash (rather than the door-divet and single-wash), and VERY HOT water in copious supply, the spray-tube did a good job. I even learned how to be adventuresome and get fry-pans and serving ware clean in the lower rack. The hydraulic physics of the spray-tubes seems counterintuitive--but water went everywhere, and most everything got clean, believe it or not.
That said, I wish they would have kept the top rack of the fifties machines and not opted to put a ridge of fixed tines up the middle in the '64; this made loading deeper pots and such nearly impossible (nor mixing bowls). In the older machines, the top rack was a nearly flat hump, minus the tines, and the loading for odds-and-ends was more flexible.
The situation for tumblers was grim. If you use a lot of tumblers and not teacups, you pretty much lost your top rack to them; even though you had a full top rack, tumblers ran up the sides and formed an array that reached the sides of the rack, making fitting much else (beyond Glad-ware that could nestle between the bottom of the glass and the side of the rack) impossible.
These were definitely dish---not ware-- washers. Water sent to the silverware basket (though generously sized) was not entirely adequate. But on mine, the self-cleaning pop-up filter worked well and shed most of the food down the drain; I never did anything special to prep the dishes, and everything came out sparkling. Of course, I didn't put baked-on stuff in, but that was a ludicrous proposal for most dishwashers of the time, anyway. (At least soak the thing first.)
The machine was very quiet, and reminded me of a soft rainstorm when it ran. The massive reversing impeller shoved a huge amount of water up to that tube (evidenced by the monstrous feed hose, similar to a radiator hose from a '54 Pontiac), and mine had big slots cut out of it that must have sent ribbons o'fury spiraling around the machine. The drain phase of the cycle could fill your sink with water, and I'm convinced that fire departments borrowed spray-tubes to fight high-rise fires from the ground.