I use a lot of hang-on stands with screw-in steps. However, they're still not fool proof, and the most dangerous aspect is climbing in and out untied. This simple prusik knot solves the problem and only costs a couple of dollars per stand: http://www.animatedknots.com/prusik/index.php
Simply tie the heavy main line at about the seat level of your stand and run it straight down between your steps. Tie it off on the bottom step with very little slack and attach the prusik knot loop. The loop gets tied to your harness or belt and you simply slide it up or down as you go. Should you fall, the knot will grab the line to stop you short.
Remember, nobody has ever been killed from a treestand fall... it's the sudden collision with the ground and branches that causes problems. [:D]