Personally, I find the Dualshock 4's control sticks far too short and can feel a little sluggish, as well as a bit slippery doe to a lack of textured top. The FPSFreek stick extenders alleviate both problems at a very reasonable price. The sticks snap on easily, add about 1.5cm to the height and have a high grip soft rubber top.
While I can't imagine using the DS4 controller without these extenders, I felt I had to knock a star of because after 4 weeks or so, the sticks start popping off during (admitedly strenuous) play, so I ended up supergluing the extenders onto the controller sticks permanently. Despite this, I would highly recommend these extenders.