I have about a dozen or so scopes with illuminated reticles made by Leupold, Hawke, Vortex and Sign Sauer. For me, they are a requirement for my hog and bear hunting when I'm expecting my shots to be around sunset or in the hog hunting scenario, well into full darkness.
All my reticles are limited to either duplex or #4 type, however. I DO NOT do busy reticles. As mentioned above some practice with brightness settings will be very useful, as the darker it gets, the more dim you'll want the reticle to be (my preference). I find higher brightness settings to only be useful during full daylight.
Some don't like the idea of illuminated reticles, but I am completely sold on them for extreme low light conditions. I will say, though, I don't necessarily feel them necessary for typical deer hunting, but I'm certainly not adverse to using them for deer hunting either.