I try to get in before its light. I find by the time I'm in and set up its probably 5-10 minutes before it gets light enough to see(not shooting light), probably another 15 minutes or so before shooting light. I don't like to be in much earlier than that, especailly if doing an all day sit, just get wore out.
I watched one episode where winke talks about what time he enters his stands and it showed him going in in the mornings. I was shocked to see him often times walking in when it is plenty light enough to shoot.
Personally, I can't stand walking in in shooting light, feel like I am just going to get busted. Walking in in the dark I have plenty of times walked as close to 20 yards of deer feeding etc. Often times it doesn't seem to bother them, they are aware I am going by, but don't know what I am. Sometimes you just see them stand on alert, or are curious, or may even bound off a few yards, but rarely blow and completely spook out. Even with a light, they don't really spook. During visible light, they would be gone. To many times I have had deer come by just as it is getting shooting light that if I had been just then walking in surely would have spooked out.