I've never had a bike locker, but I'd jump at the chance. I have a large trunk on my rack, that I keep all kinds of junk in, gloves and lights and spare tube. I thread my cable lock through a plastic tab on the trunk & through the seat, which protects it from the casual thief. The contents are not secured, and while they are not valuable, it would still bite if they were stolen. My rear wheel too, is not secured, just not so easy to walk off with.
Since I live in a small midwest city I don't worry about it too much, but I am always aware that those things are not secured.