So either the Quality Department is not the point at either Amazon Sensei was delivered from a bad batch. In fact I had to replace 2 times to finally have a proper mouse ... and again, "okay" is not the right word ...
The first copy I received the knob which began to creak unbearably after 2 weeks. So I asked a replacement by Amazon.
The second was a problem with the left click, which offered no resistance (to have the finger was simply placed over the mouse click) and often the button does not return to its original position. Return to sender ...
The third was good but the mouse hangs heavily on my mouse pad ... the same brand (Steelpad 4HD), a straw! Less problem even the surface of my desk but still some very annoying clashes.
I finally ask for a refund and I'll try the Razer Taipan hoping that it is better.
In history we note once again the quality of Amazon superb service. It is a real pleasure to have such a reliable customer service, you can make purchases with confidence! Thank you Amazon!