Just a chime in from a former Sears dishwasher technician ..... Most problems I saw were due to a coule of simple things:
-- Water not hot enough. Most people don't keep their water heaters at a hot enough temperature to melt grease. And they throw dishes in the racks, set the controls, and hit the start button. The hot water, which isn't hot enough to start with, takes a bit to warm up (usually). So it's coming in cold to start, into a cold tub filled with cold dishes. It's not hot wnough to dissolve all the soap, much less the grease.
Run the water in your sink until it's good and hot before starting your dishwasher. Use the pre-rinse cycle to let the water heat the tub and dishes before the machine opens the soap dispenser. You may have to use the heating element. You may have to temprarily increase the water heater temperature.
-- Pre-rinsing the dishes almost spotless. Your detergent is formulated to bond with the grease and take it down the drain. if it dosn't have grease to bond with, it stays in the water that stays on our dishes. Especially if you have hard water (I'm in SW AZ, and our water is best described as liquid rock!! You don;t want to look in your glass after the ice cubes melt!), this will leave spots on your dishes.
Scrape off the big chunks and put the dishes in the machine. After all, it's the machine's job to wash them, not you, right? Okay - hard dried stuff may need a hammer and chisel; other than that, see (1) above.
-- Clogged holes in the sprayers or poor dish arrangement If the water won't spray or can't get to the dish, it won't clean it. To check the nozzles may be a bit messy: the best way I found was to start a wash cycle and the quickly open the door. You can usually catch the water losing pressure from the holes in the sprayers. No water may mean that hole is clogged. A cup of vinegar can help with deposits. Occasionally you'll get a dried pea or such sideways inside a sprayer.
Just my thoughts, and worth every penny you paid for 'em! 8>) Ed