The rim system in the pads. Sure it works, but its just a plastic o-ring with a thin bit of rubber attached and feels flimsy and plasticky when you hit it. Roland/Yamaha pads both have a stronger and sturdier solution. The 2Box pads are great, but imagine how good they would be with a proper rim system that you can really dig into...
the rim system really could use improvements.
firstly, the triggering is very uneven around the rim.
secondly, the rim system is manufactured from very lightweight plastic and rubber. i've just dismantled my snare drum to find that the rubber has split and the hard clear plastic inner ring that transmits the hits to the sensor has cracked. i'm not a heavy hitter, and i use quite light sticks (11As). i do love my rimshots though!