I started off with the original Darbee (on my JVC RS600 projector) and later used a Lumagen video processor that includes Darbee processing.
Ultimately I use Darbee processing very sparingly, usually not at all for movies. I find it produces a certain identifiable "look" to the image, almost if a bit of white spray paint starts covering the image. I find that the contrast/sharpness enhancement feature on my projector actually works better for a perceptably sharp image but without the more obvious Darbee effect.