I just installed an automatic pop door and I luv it! It is on a timer and has worked flawlessly. We are out of town from time to time and all we need is for someone to collect eggs. The feeder holds food for 5 days and the automatic water-er holds 7 days of water, so the galls really don't need any help when the DW and I are out of town for the weekend. It is amazing how many friends and neighbors will volunteer to collect eggs, whereas getting somebody to come over to take care of the chooks is almost impossible.
My door opener is the Add-A-Motor D20 Chicken Coop Motor and this thing will lift just about anything. The lift cord it comes with looks pitifully light, but the motor will pull the line clear through a 1/2 inch plastic rod I used to attach it to the pop door (I accidentally reversed the polarity when attaching the timer and didn't pull the plug quick enough). I have a good sized, sealed, 12 volt battery charged by a solar panel. My chicken tractor is in the shade of a large tree but there is enough indirect light each day for the solar panel to keep the battery up.
I have the American Hunter FeederMax timer that I have only one complaint: There is no way to attach it to the wall. It runs off a AA battery, which is loaded through the back, meaning you can't mount it to the wall without blocking the battery access. The wiring harness that comes with this timer is VERY good and will allow just about anything to be hooked up (lift motor, battery, solar panel, another remote motor, and a spare remote plug on the battery lead). With this wiring harness you will NOT need a terminal block for hooking up components. Great little timer but I'd like to mount it to the wall (BUMMER!). I'm also a little concerned about knowing when that AA battery in the timer will crap out.
8 out of 8 hens in my coop luv the idea that they don't have to wait for that bum of a caretaker to crawl out of bed on Saturday and Sunday mornings to let them out of the coop. And I feel a lot better knowing that they are behind the pop door each night no matter how late I get in.