Well, Kittyboy now falls into that category. We have no communication as far as the concept of "big-boy bed", he's only 20 months, falling asleep is not always easy, and waking up is often distressing. BUT, he is SO capable of escaping his crib. Standing in his crib, with the mattress on the lowest level and the side raised completely, he can put his foot up to the top of the rail. He just hasn't followed through yet. No doubt, though, he's strong enough that it wouldn't take long!
So, next payday we're getting a toddler bed, if I don't get one through Freecycle first. In the meantime, we're ensuring he doesn't climb out of the crib - the mattress is all the way on the floor! I just don't know what we'll do about keeping him in a bed without sides long enough for him to actually fall asleep!
We'll see how it goes!