Product review (2 stars): Whirlpool living up to their typical standard
I bought a house that has a Whirlpool dishwasher in it that uses this rinse aid cap.  Just like every other Whirlpool appliance I have experience with, the dishwasher's performance is mediocre, so I ran a few loads of dishes with the Sani-Rinse option enabled to see if it would improve the thoroughness of the rinse cycle.  After running a few a loads this way, the rinse aid cap started to leak it's contents down the door of the dishwasher between loads.  Since the Sani-Rinse option apparently uses hotter water, I assumed the hotter water had caused the plastic in the old cap to warp or shrink, so I ordered this replacement cap.  I paid this item's ridiculous price because it was a legit part, and it came packaged in a bag that was labeled Whirlpool.  It did indeed stop the leaking...

...for 10 months.  Now this cap is also leaking, even though I haven't again used the Sani-Rinse option.  Perhaps that means that the Sani-Rinse option warped the plastic in the door, rather than the plastic in the cap?  Who knows, your guess is as good as mine.  Regardless, in my experience this kind of performance is par for the course for Whirlpool, and is just further justification for why I will never voluntarily buy a Whirlpool appliance.

UPDATE:  I've used Earth Friendly Product's WaveJet rinse aid for years, and is what I was using for the entirety of my experience in my review.  However, I recently saw that Lemi Shine had introduced a rinse aid, so I got a bottle of it to try.  I've now run two loads of dishes through my dishwasher using the Lemi Shine rinse aid, and it hasn't leaked out.  So I've upped my review for the dispenser cap by one star, since it apparently doesn't completely suck.  At least not yet...