Our water is fairly soft so initially I didn't use the softener function but thought I would give it a try and see if it improved performance.  (That would have been hard to measure since the Miele always gave absolutely spotless results except for once when I put in the rack from the grill.) The whole bottom of the tub was covered with a white film after the first load.  The dishes and pans were cloudy as well.  Once I adjusted the softener function to the minimum level the film disappeared.   Since then I've discontinued using the additional softening.  I have always used either a Finish product or Seventh Generation detergent. 

I had a bottle of Jet Dry tip over and leak inside the cupboard once, leaving a blue stain that I never was able to fully remove.

Malcolm - Any updates on your problem?

I use quantum tabs, finish powerball and even the old ElectraSol tabs with phosphate all the time but don't bother to change the detergent setting.  don't see much difference in cleaning performance with the tab setting, but I have an older LaPerla

Is this haze something that can be wiped off with your hand?

Does you model have the water softener?  If so when was the last time it performed the regeneration step?

what's in it? a mild acid? I wonder if citric acid would have done the trick. I descale my washer and dishwasher four times a year with 1/4-1/3 cup of citric acid powder. My main objective is primarily descaling of the pump and plumbing inside the machine, and secondarily to shine up the SS interior, though to be honest I never get any visible residue or scale inside the machine (Bosch).

Oddly enough, I have friends in the same town (same water system) with a high end KA, three years old maybe,  and they always seem to have scale in their SS interior. They chose KA over Bosch because of KA's food disposer; at the time of purchase, they still had three kids at home, though today only one is still in high school. However, their old, poorly performing DW was so bad that they had to pre-rinse everything, so I doubt if the KA's disposer even gets all that much business. But I think a concern was if the kids threw in dishes that weren't scraped or pre-rinsed (never happens, mom pre-rinses EVERYTHING).

They gave up using Finish tabs because their detergent dispenser door wouldn't always close securely (tabs were too thick for door to close) and I think are using liquid. I advised them to use powder over liquids if the tabs didn't fit, but I think they use liquid (and they recently gave me three giant Costco canisters of Finish tabs which they can't use). Their DW always has scale on the interior, even with descaling with citric acid (I gave them a container of it as a thank you for the Finish canisters). Their dishes do come out clean. I am not sure if they use JetDry but I think they do use it. I can't figure out though why their interior always looks terrible, even after the end of a cycle.

Thanks for the tips re: Lemi-Shine. Never heard of or have ever seen the product, maybe it's lurking on the hardware store's shelves and I just never noticed it. I gave them a large jar of citric acid and that did not help. I wonder if maybe their KA has a "matte" rather than shiny SS finish. I don't remember peeking at it when they first bought it, but as an occasional dinner guest in their home, I help with the dishes. At least the DW gets them clean.