If you're serious about your PC gaming, you've already heard of SteelSeries. You might remember their first high-end mousepad (excuse me, "mousing surface"), their headsets, possibly even their highly-acclaimed Xai gaming mouse. Lately, they've been going hard with licensed gear like their Diablo III mouse and headset, but with the Sensei, they're going back to their professional gaming roots. This mouse is intended to replace the Xai, which means it's only for the best of the best. (Of course, the $90 price tag already told you that.)
You can also control the lift distance, mouse acceleration/deceleration, and set the drivers up to fine-tune (or eliminate completely) any mouse path correction functions. What's more, you can load your profiles onto the mouse itself, so if you want to bring your mouse to a gaming event, it'll keep your exact settings without having to install any special driver software. There's a small black-and-white LCD display on the bottom of the mouse that you can use to change mouse profiles on-the-fly, and it'll show your image of choice when it's idle.
Like any good gaming mouse, you can configure different profiles for different games and applications with the included SteelSeries Engine driver software, which lets you change your 7 button assignments. You can even develop some pretty in-depth macros that track timing and include keystrokes, though those probably won't be tournament-legal for your game of choice. You can also track your mouse usage sessions to see which buttons you use more often than others, and change the colors and brightness of the built-in lights. You probably won't actually do much of that stuff, but it's kind of cool to know you can if you want to.
The Sensei won't revolutionize your game overnight--at least, it didn't revolutionize mine. (I suspect this is because I spend too much time in the office and not enough time playing games.) So far, though, it feels like the design and customizability are perfect for someone who is willing to spend the time in the lab playing with the different settings to make it feel just right. We'll dive deeper into the driver features and tweaks in the full review--stay tuned!