Summary: We upgraded all our macs at work recently after the old macs were stolen and they all came with this mouse. The tracking on these is terrible there is a definite lag on these when moving on most surfaces. this makes it very difficult to do any kind of precision work.
Pros: It can be replaced.
Cons: Terrible tracking on most surfaces razor sharp edges scrolling sucks because of finger friction on the mouse. the entire thing is a track pad causing your work to constantly move all over the place every time you move your hand or fingers on the mouse.
Cons: Barring OEM, this is likely the worst mouse I've ever used. Uncomfortable shape, awkward gestures, no middle-button functionality barring a hack; this mouse does it all. If I were Apple, I would be embarrassed to sell this product.
Summary: Yosemite has a bug where in the bluetooth mouse stutters and there is no fix for this. On searching the web that loads of people are facing this issue. I've tried all the suggested solutions like resetting the PRAM and upgrading to the latest version of Yosemite (10.10.5).