One of few things that can make me mad.

Horrible. The first month was good... but then it started having problems. Not just a few problems either. The battery suddenly decided to crap out on me, so it only lasts about 10 seconds after not being plugged in before it starts blinking the "charge me" indicator. Then the scroll wheel stopped clicking when scrolling down, and got really loud for scrolling up. This makes it impossible to scroll only one "click" down, so is useless for games that use the scroll wheel, and on top of that it scrolls on its own randomly. The mouse can just be sitting there on the desk not being used and start scrolling one line at a time through a web page. The Bluetrack or whatever sensor cannot track on any surface that is not perfect, I mean PERFECT. It just jumps around everywhere or just does not move the cursor at all if not on a clean black mouse pad with a very even surface. But even on that sometimes it does not recognize it at first, I have to click the buttons a few times to get the mouse's attention. Also, the third side button and square "games" button cannot be remapped for a different use, at least not with Microsoft's software. If I had to say one good thing about it, it would be the fact that you can turn it off so the lights don't blind you at night. HUGE disappointment.
I FINALLY get to replace this piece of **** with a Logitech g9x this weekend.