We use an automatic door. My wife built it out of a car antennae and a piece of plexi. It's on a timer which we change slightly with the season. Works great. It's amazingly wonderful not to have to close the coop door each night. Totally worth it.
We wanted to install a secondary door in the coop and just for fun we bought one. I can't remember the company but it is a lightweight steel door that goes up and down depending on the amount of light. It's nice and it's worked well for us so far. We're able to leave them overnight, which is great. We can go out and be assured that they'll go in when it starts to get dark and their door will shut.
Now, this isn't to say that I don't go out at night at all. I'll check the automatic doors once a week or so to make sure they're down, and I check the chickens every morning and make sure the door is up.
We researched making our own automatic openers around 10 years ago, at that time the sum of the parts cost more than we could source a ready made unit. We have used the VSBi unit since then and it seems that the technology and components haven't changed much at all, and with the component parts becoming more available and cheaper then I'm sure we could make our own more competitively. I think we'll look into this again next year.
For information, we fit all of the openers inside the Hen Houses to keep them out of poor weather, after all they are electrically operated even if it is by battery.