That poor Voyager!!! I can't believe how bad that was?! I wonder if they had some kind of buildup before using that gel, and the gel made it that much worse.
I've been at the point for the past five or so years that I'd never put powder or liquid gel detergents in my dishwasher again. Years ago, powders were the manufacturers' flagships, so all their premium ingredients went into them. Now, powders and liquids are primarily BOL and cheap, and I've seen with my own eyes what using them does to anyone's machine. I've been on my mother-in-law about using Publix and Kroger brand "lemon" gel in the new Maytag, and even in her old Whirlpool at the old house (I'm talking like a 1970s era WP Imperial, beautiful machine I might add) and after bringing some Cascade and Finish pacs/tablets, she finally saw the difference I was begging her to see.
There have been a few times I've bought a small box of Cascade Complete powder, primarily when I was using the PowerClean, just to throw a dash in the prewash for extra dirty loads, but the few times I'd try using solely the powder, my plastics would feel gritty, and the racks themselves would feel "chaulky" to pull in and out. With the Maytag Voyager I had and now the new Whirlpool, I haven't had a need to try any extras. Surprisingly, despite my WP being TOL and having a diverter, there is no Top Rack/Bottom Rack Only option, perhaps because it uses so little water anyway, and those options only used to shave off 10-15 minutes from the Normal cycle in machines that have had them in the past; if I wanted to run a half load I'd still only be using about 2.5 gallons and the timer would knock down to under 2 hours because of low soil levels.
Pacs and tablets for me are the only things I'll touch now because A) they are usually complete with rinse aid and protector agents for dishes and the machine both, and B) because all modern dishwashers are being designed specifically for use with them, which explains the shapes of the cups like in my WP and John's GE.
As far as the fixed dose for unitized detergents, I myself haven't really had an issue because I only ever wash full and dirty loads in the dishwasher. Laundry detergent pacs, on the other hand, don't do well for me simply because there are so many variables with laundry. You can have a heavily soiled but small load, or a large load that isn't very dirty, but the soil level isn't as easy to determine on clothes as it is with dishes. Every time I try a tub of Tide pods or something similar, I end up with a washer full of suds even with a large load of clothes, or with no fizzing in the water at all and a question of "was this enough detergent, do I need to toss in another and then have too much, why do these clothes not smell as "scented" as the last load", where powders and some liquids are much easier to adjust per circumstance.