I've got one of those Blade Safes on my chefs knife and consider them to be relatively inconvenient as compared to a sheath type guard or a block or a magnetic unit. It pretty much requires two hands and contortionist ability to unlatch the cover or a third hand unless there is a method I have not yet figured out.
In absolute terms, it is only a second or three longer to get into action so it is more of an annoyance that a real problem unless you happen to suffer from arthritis and have some limits on your dexterity.