I love the simulated click sound with the scrolling, I often find myself just spinning the ball for the clicking.
You have to be careful with the double programmable buttons, particularly with games, having set them up then jumping into ME3 I hit all sorts of trouble. :S One problem I have with the programmable buttons is that they have no repeat options for keyboard presses, I'm not even concerned about repeat rates I'd just like it to repeat like normal. Mapping one of the tops buttons to a keypress and then mapping that keypress to 'hold to run' in a game just does not work. It seems the slimblade won't register keypresses until the upstroke of the button press.
Clicks work fine in that you can hold them and they register, it just seems to be isolated with mapping keypresses. I found clicks for that sort of stuff better anyway, and then aiming and shooting with shift and space, makes tracking a target so much easier.