John Shriver , Oct 11, 2010; 10:32 a.m.
The cons of all the powder C-41 kits are that Blix (bleach and fix in one solution) is a bad idea. You wind up with a very unstable solution, that will fail quickly.
They were designed for a press photographer working in the field who had to get out a processed negative as fast as possible. Getting the best results was not important, nor were the keeping properties of the chemicals.
Best results come from using the Kodak or Fuji-Hunt chemistry. Nobody else can match them, due to patents and shared trade secrets. However, they are hard to source, and a pain to mix, you need to mix parts A, B, and C of the developer, along with developer starter. Part C is unstable in the bottle after you open it, it's very sensitive to oxidation, they backfill the bottle with nitrogen at the factory, but that's gone after you open it.
One alternative is to use the developer from the Unicolor kit, but buy Kodak Flexicolor bleach, fixer, and final rinse. The bleach is expensive, but it lasts and lasts, especially if you use an aquarium pump and bubbler stone to put oxygen back in it. The fixer is the cheapest fixer in the world, and is great. Final rinse is also cheap.
You can also buy small quantities of the Kodak developer from Photographer's Formulary. They are re-packaging it into smaller bottles, and presumably backfilling part C with nitrogen.
There's a lot of discussion of this topic on APUG.