Using left, top positioning to move the slider elements causes a performance bottleneck as the layout has to be recalculated. More detailed article here: http://www.html5rocks.com/en/tutorials/speed/high-performance-animations/
Instead using transforms will make the transition smooth. Check out the video in the article above.
This is quite visible on mobile phones, where the slider transitions are not smooth, and the FPS drops noticeably.