They work great,
This review is from: Grip-iT Analog Stick Covers, Set of 4 (Video Game)
I got a set of these last week and it took me all of about 10 minutes to put them on my two controllers and since then I have been really happy with them. I was concerned at first that they would just slip right off but after using them for gaming over a weekend (playing about 5-7 hours) they have stayed on and in the exact spot I initially placed them. I am really happy with my purchase.