Regarding the Sensei,

EXACTAIM: SLOW DOWN AND FOCUS
SteelSeries ExactAim will allow you to be more precise. Headshots anyone? As you slow down your cursor the mouse will decelerate even more allowing you to focus on your target.
EXACTACCEL: MOVE FAST, NO EVEN FASTER
SteelSeries ExactAccel does just the opposite as ExactAim. As you increase the speed of your mouse movement, ExactAccel will accelerate your movements even faster in order for you to move across your game or page faster.
Did they really just break mouse acceleration into two separate components and market them as amazing advancements in gaming? Not only is acceleration incredibly old news, it is also terrible, and they are terrible for doing this.