I got an email about the mouse and thought I'd write a little review about it.
I bought the Sensei about a year ago now, and I've loved it more and more every day that I use it. The 'aluminium' top is actually plastic coated in paint which many people say wears off, though the only wearing I've noticed is right at the bottom at the back of the mouse, and even that is barely anything (and for the first few months I had a low desk so I was constantly banging the mouse).
The sensor on the Sensei is amazing, though if you're going to get it, have a little cotton bud or tiny (and very soft) paint brush handy as anything on the laser will throw the mouse off. I had a cat hair stuck in it once, and though the mouse didn't play up like crazy, it was a tiny bit jerky which made sensitive games like Skyrim horrible, so just be aware of that.
The colour options on the mouse is crazy. You can have the 3 lights all different colours (the dpi light has two settings) which though it may sound silly, is quite nice. When I had my cheap pc, I bought a case with red LEDs. No problem, set the mouse to red. Bought my new Antec 900 with blue LEDs, still no problem, changed them to blue. I'd like to note that WHITE does NOT work on the Sensei. As the LEDs are multi-colour, there's a pink that bleeds through causing white to ACTUALLY show a very bright pink.
The side buttons are perfect for me. There were people saying they kept hitting them with their pinky etc. I've had no problems, so I'm guessing it really depends on your hand size/shape and grip style. For reference, I have medium sized hands and play with a palm/claw mix. The ambidextrous shape of the mouse is actually surprisingly comfy and I absolutely love it.
The wheel has a nice click to it when you use it, and it doesn't seem to wear out too fast either (touch wood!). I used to play Counter-Strike and used the mouse wheel to bhop (CS players will understand!) which uses a LOT of wheel usage and it still sounds, feels and works just like new.
The cord is braided which I don't personally like, but I've grown to get used to it. My old desk was wood with the back of the keyboard tray NOT painted so there were splinters of wood all over the place which has ruined a certain area of the cord braids, so make sure you have a smooth surface all round with the cable!!
As for the extra on-board features, I don't use any of them, but it's still nice to have that option. The ExactLift function is great, as I can set it to the lowest possible setting and it still works flawlessly, meaning if the mouse is even 1mm away from my mouse pad (SteelSeries QCK) it cuts off, making low sensitivity games such as Counter-Strike great.
This turned into quite a long review didn't it... Well, you get the jist of things. This mouse is simply amazing, my best best of all my PC gear.