Very hard to select text via mouse accurately after upgraded to Yosemite After upgraded to Yosemite, I've found that the mouse selection is basically broken, e.g. when I select, I follow the steps


mouse down, start select
end select, mouse up


The problem is, when I mouse up in step2, basically what I selected, has 50% of chance is being unselected.

I can't reproduce the issue every time, but given that 50% of chance, it is very annoying.. 

Any idea?
regardless from the type of mouse you are using, try going into settings/mouse options and feel free to fiddle with the settings here, when I had trackpad tracking issues after the update (couldn't even move the pointer arrow properly), I just went there and changed the cursor sensitivity and that did the trick.

Hope it works for you too!