Something is missing the finishing touches.

I've been here for over 17 years and gamer precision mouse is one of the most important things for the game.
For years I put on Logitech, even if they bring every now and then sometimes bad devices on the market.

My opinion about this mouse is split:

The Buttons:
The size of the mouse equivalent of my MX518, yet it feels small. Too small.
Why? Because the buttons are clearly further back to the left and you thus have to start the hand later.
When MX518 I could easily put my hand on the mouse and use the thumb nor the two side buttons.
When G402 I may either hand does not put on the mouse or must renounce the use of the rear-left button.
The precision buttons are front left with the index finger also very cramped reach .. They could well half a centimeter can be more right.
Well, I'm playing in general hardly Games where I had to prove a lot of buttons, so this is not for me tragic.

However, not all buttons are bad. The DPI shift button (bottom left) are very easy to operate with your thumb.
The function while pressing to have a reduced speed is very convenient.
The left and right mouse buttons are nice and long, which is pleasant in my long fingers.
The pressure point of the keys is generally very good.

The wheel is a negative point for themselves:
It grinds quite loud and can be pressed only very sluggishly. This can sometimes end in accidental movement of the mouse.

The lubricity is split again:
But it has a little less frictional resistance than the MX518 .. makes up more noise.

Precision:
Here shines the mouse. The most precise mouse I had before. No plasticizers (Smoothing), no acceleration, just reliable precise cursor movements. Just so must it be for a FPS gamer.

Conclusion:
I think for now I'll stick with the MX518, simply because I can put my hand on it. So many times I come lately anyway no longer to play.
The mentioned disadvantages are certainly perceived to different extents for each, so I leave the weighing times you.