in that aspect they are awesome, what I hear is that the roughly 1 1/2" thick buckle sometimes gets between the helmet and shoulder/collarbone area and limits your head motion. it may have been from people wearing it incorrectly, cant say I have any FHE with them.
the blackstar bag uses a similar strap but has a heavey duty plastic buckle that is much thinner. it also has 2 D rings that tighten and loosen the strap easily and a cross strap to keep it moving around that can attach at two different points.
the thing is you have to wear the bag with the buckle in the middle of your chest, if it moves too much then yes you have problems the way to avoid this to some extent is to use the secondary strap that holds the main strap on your chest, its not perfect and if you load the bag very full and heavy nothign will stop the buckle from riding up toward your shoulder.
the better bet is to get one of the rolltop bags from chrome (i have the one called the Ivan model), they are waterrproof, hold a litltle less but are extremely stable, as they are a backpack configuration and have both a waiste strap and buckle system and also a chest strap that holds the two shoulder straps in place, in a word once this thing is cinched down its not moving no matter how fast you go, the tough part is when you need to take it off you have to undo all of this.
