Not Idiot Proof...
Doesn't bleed the air when turned off
This On/Off (in my humble opinion) is one of the coolest things I have seen. Sure, it is only and ASA, but I really like the push-button style. Unfortunately, when you turn it off, the air doesn't bleed, so the tank doesn't come off any easier, but it surely saves your O-rings. The biggest problem with this is that if you don't turn it back on after removing the tank, the marker will hold one or more shots worth (depending on the marker) of air that can easily be used to fire a paintball. What does this mean? This means that someone who doesn't have as much respect for their marker as most people do could easily forget that fact and end up shooting someone even though "there wasn't a tank on it", or someone else could toy with it thinking that its safe because "there wasn't a tank on it" and hurt someone. I personally don't find it a huge deal, for I am very big on safety, but it could be a problem to someone younger or not quite as careful.
Its a great product with a minor flaw, but I personally don't think that flaw is big enough to hurt the rating.