Mouse=control and control requires context. Here's mine:
I've never really felt a need for another mouse after I upgraded from ball mice to the Logitech MX518.
It is a right handed mouse that is not too big like most mice, in particular Razer mice which tend to be huge. This is important since many old-school competitive gamers do not control their mouse from the shoulder but completely using only their fingertips. This requires a small light slippery mouse with high DPI.
It is an optical (LED) rather than laser mouse. While this means its sensitivity maximum is likely to be far lower, it also means the on-board DSP does not need to be as complex to interpret movement against a large variety of surfaces unlike a laser. After all a typical gamer knows that the mouse surface is just as important as the mouse and will typically obtain the smoothest and most uniform surface available to them anyway. Why is this important? Well, for example, I bought a Logitech G5 laser gaming mouse for another PC and while it had all the usual laser advantages against any surface and high max DPI, the cursor also occassionally and temporarily "stuck" for unknown reasons even on a smooth pad. No such sticking ever occurred even once on my MX518 on the same pad (Func Industries Surface 1030).
It has full sensitivity control via extra little buttons above and below the middle scroll button.
Its feet/pads are unbelievably smooth and slippery - even more than the Logitech G5.
It is lighter than the Logitech G5 (excluding the additional weights which can be added on the G5).
It has two buttons on the left (thumb) side rather than one button and a wobbly scrollmouse like the G5. These are unbelievably useful buttons because in combination with the middle button can be used to put all keyboard modifier keys on the mouse (shift, alt, ctrl) and therefore easily triple the number of available controls in many games (especially World of Warcraft). Or the buttons can be programmed with most games or via Logitech bundled gaming software or the free XMouse to do anything.
It's amazing how a five year old mouse still beats the pants of most new devices :)
Of the reviewed mice, only the Razer Imperator and Deathadder look suitable for my needs (assuming they are not too big) and I'm fascinated by these "adjustable thumb buttons" of the Imperator - I will have to read more about them elsewhere!