We just reinstalled our DMR77 after our kitchen renovation, so it was a good time to figure out if a thorough cleaning would improve wash performance. My main complaint is that the filtering system performance seemed to have degraded after a year, and we often get little bits of dried food on plates and glasses (and yes, we do use a rinse aid). The Sears tech who came to replace the upper rack adjusters recommended Dishwasher Magic or Glisten powder to bring performance back, since the spray arm jets or the filtering system might be clogging up.
An interesting post on Lifehacker (referencing another post on Real Simple) said that using a packet of unsweetened lemon Kool-Aid was a great way to clean the insides of a dishwasher. This is due to the fact that the main ingredient of lemon Kool-Aid is citric acid.
After a little research, I discovered that not only was Dishwasher Magic and Glisten made up primarily with citric acid, but so was coffee machine descaler. Since I had some packets of descaler for my espresso machine, I thought it might do the trick.
After cleaning the thick layer of black tar-like gunk from the bottom of the door seal (disgusting), I put one packet of descaler in the detergent cup and closed it, and put another half packet in the tub, then ran a normal cycle (with an empty machine, of course).
The results were pretty good, and the first load came out with no food particles stuck to anything. We will see after a couple of loads....