Arrives tomorrow, will report back.
The mouse is SMALL, even smaller than my Logitech Anywhere MX, which already is a tiny notebook mouse - doesn't bother me much tho. Both the main buttons make a nice soft click sound, the wheel doesn't rattle and works very well. The two blue LEDs (illuminated wheel and battery indicator) are a nice eye catcher but I turned them off completely to conserve battery. 200% better build quality than the Microsoft 5000. The 2.0 Mac driver is pretty good at well, it lets you customize everything, really nice.
Anyway - this "sleep" problem is there and its definitely annoying. The mouse enters a power saving state after not moving it for exactly 3 seconds (it even does that if you move the scroll wheel within the 3 seconds, you HAVE to move it to prevent it from snoozing). Then, after 3 seconds, if you move the mouse it needs like half a second to wake up and the cursor jumps from the "where it went to sleep" position to the current one...
I can see how gamers that are moving the mouse around all the time are unaware of this issue - but for everyday use, like reading a longer webpage or doing some basic desktop work its a deal breaker... (for example clicking into the text field here to correct a typo, moving my hands to the keyboard and back to the mouse > it SLEEPS already) Everything's fine if you use the USB cable that comes with it, but I wanted a BT wireless mouse... so it goes back to Amazon, gonna try the Logitech m555b now.
Verdict:
High build quality, great Mac driver, feels good to the touch, LED gimmicks, USB cable, works out of the box
but
very small (smaller than common notebook mice), heavy (some might prefer heavy mice tho), SLEEP ISSUE which kills the whole usability for non gamers