Incredible! This mouse is a must have for anybody that either is a multi-tasker, a photographer, a gamer or simply somebody who wants a very durable and high quality mouse. My brothers still own its predecessor, the MX Revolution, and it has now been 3 years.
Unifying technology is great if you have many Logitech wireless devices, such as keyboard, mouse, headset, etc. Lets you use many devices on 1 USB port and there is no interference.
Customizable buttons are ingenious (can be set to copy/paste-which is very useful for multi-tasking) and well placed. The hidden thumb button is great for changing the DPI settings (my own settings that is) when either gaming or using Photoshop, or any task that requires fine tuning.
The wire can be plugged right into the PC to recharge the battery (lasts about a week I think), or you can use the extender and plug is into the wall.
Superfast scrolling on/off is very useful, no, extremely useful for internet browsing, music database searching, etc.
The ergonomic thumb area is not as good as the Revolution MX, for your thumb is not completely against the mouse. Furthermore, some people might say it squeezes the thumb because of the zoom button's edge, but really, it is FAR from being uncomfortable.
Of course, Darkfield... Works on transparent glass and often better on any surfaces other than mousepads.
Yep, might be expansive for a piece of electronic but you won't find anything better for a PC, and since it's not a ''gaming mouse'', you won't pay for the cheap materials normally used on ''gaming'' devices (so cheap, really!).
**EDIT**: 2 years later, still works, except that the left click button is broken (sometimes rapid-fires. Apparently, this is a common problem with those cheap click buttons...