It's been almost a year with the same batteries in it, I wouldn't say it's slow to open. I read the reviews also and me personally, I love it! And the red matches my coop:D :woot :woot
I don't use sand either, but there is dirt and what not around. This is the door I use and have had no issues with it, easy to use and runs off 2 AA batteries that I have not replaced yet. Keep us posted what you decide on:D...