use Rinse Agent?
Do I use "Jet Dry" or other rinse agents? Yes. Do I need to? No.
It's not so much the brand of the dishwasher, Whirlpool has no special abilities when it comes to anti-spotting, ha. It's water chemistry as in hardness (=calcium carbonate, aka calcite, aka lime)
Many spots are hardness deposits. Rinse agents reduce the surface tension and the water with the calcite content will run off the dishes before the water evaporates and leaves behind its mineral content.
Alcohols tend to go into a vapor state at lower temperatures than water, so at least the alcohol component of the rinse agents (and alcohol based compounds tend to be the primary constituent) will evaporate quickly and not leave a residue that you can consume.
By the same token, as there are microscopic food particles in suspension in the rinse water, they should (at least in theory) "sheet" off with the rinse water and not remain behind when the water evaporates, in the presence of a rinse aid. So even in soft water conditions, dishes should be cleaner (at a microscopic level).
No matter how good a dishwasher is or how effective its filtration, you are going to have some microscopic food particles in suspension. So from that aspect it behooves everyone to use a rinse agent.
My water is softened to 0 grains, so in My GE tower wash dishwashers and my Maytag Reverse Rack the dishes come out beautifully even without a rinse agent. I still use one however, and do they seem to have even a higher sheen and that luxuriously smooth/slick feel to the touch when they come out.
So if you use heated dry as I almost always do and have soft water you can get by very nicely without a rinse agent. But it's nice to know your dishes are a little cleaner at the microscopic level when you do use a rinse agent.

Even though we can't see these particles with the naked eye a film of them on dishes and glassware do affect reflective light.
If you have "hard" water then you may want to more seriously consider a rinse agent, especially with some of the older dishwashers that really rinse well That sounds counterintuitive, but their more effective rinsing means less of the rinse agent, that was contained in the detergent, will be carried over into the final rinse.