I don't know if you've seen my saga with the Kitchenaid here, but I have been very well pleased with it's performance. I have found that an older high-end model will perform better than a newer bottom line model. That's what I was dealing with in my case.
I had a contractor grade Frigidaire unit in my home. It cleaned fairly well, and was quiet. The cycle times were a little long though. This dishwasher did not heat the water, and it also used a rather basic filter screen in the bottom that all the water went through for both washing, rinsing and draining. Like Gyrafoam mentioned, if food gets trapped on the filter, it will sit there until the end of the cycle, when the operator can clean it out. This dishwasher too, did not have a direct connection to the upper spray arm, and it only received water from an indirect tube that squirted it into the rack from above. Again, top-rack cleaning is a problem with vintage machines that Tom Turobomatic brought up, that still manifests itself in bottom line newer units.
There are a few big things I dind't like about the Fridigaire DW. One is the reversing motor. It only has enough kick to provide either the top or the bottom with washing power, so it switches back and forth during the cycle. This can not only be annoying, but it also makes for lengthy cycles...this DW took over an hour to wash a load. The worst part about this machine is that it is built like a child's toy, with plastic parts all over it. if the impeller, impeller seal, or the motor gets damaged in any way, you cannot replace the parts individually, you MUST replace the entire $150 unit as a whole!
I just recently acquired a Hobart Kitchenaid KD-18 that is about 30 years old or so. My "new" Hobart Kitchenaid however has seveal features above the new/old fridigaire doesn't have. The nicest thing I like is that it has direct plumbing to the upper spray arm, so the top shelf gets washed much better. The cycle time is only 22 minutes too, which is especially nice, since the machine is a bit noisier than the newer units, and you don't need to listen to it longer. The build quality is superb, and it is easy for an average person to repair... (just don't get the parts mixed up!) This dishwasher really does a good job on greasy, caked on grime too!
The advantage I see of modern higher end DW are many like:
Much less noise
Built-in water heating
Self-cleaning filters and garbage disposers
Electronic controls
The DISadvantages are:
Poor build quality and servicability
You must pay over $500 to get features that set them apart from the older machines.