For one, I love the feel of the controller when I simply hold it in my hands and do nothing with it. The problems start occurring when you actually press the buttons. There are two major issues with this controller. When using LT And RT triggers, if you press down with any appreciable amount of force, the insanely sharp corners that house the triggers irritate the fingers. The 360 controller had no such problem. Everything was rounded properly. I've never seen this issue on any controller.
The second major issue is with the LB and RB buttons. It's unbelievable that you are forced to arch you fingers to press the outer corners of those buttons. The fingers are unable to naturally wrap around the length of the button and press it from the inner portion, as apparently the plastic button cannot get enough leverage on the switch. These are major design flaws that never should have happened.