There is the aforementioned difficulty in getting the
Grip-Its to sit... just... right. However, unlike, say, screen protectors, there is no real penalty for putting the
Grip-It on not-quite-right. You can either sort of exert pressure in the desired direction with your thumb to slowly edge the
Grip-It in place, or simply remove the
Grip-It from the Analog Stick by sort of rolling it back off, and try again. Neither of these re-seating or centering methods seem to cause any damage to the rubber
Grip-Its.
I found the Grip-Its to work perfectly with the PS3 controllers, which feature Analog Sticks that are rounded outward (convex) on the top. The Grip-It Analog Stick covers easily pulled tight over these, providing an excellent grip-enhancing layer over the original Analog Sticks. However, the 360 controller features Analog Sticks with tops that are rounded inward (concave), providing a slight impression in which your thumb is supposed to "sit" ever so slightly. Of the two such sticks, I found that the Grip-It formed a slight air-pocket between itself and one of the Analog Sticks, while the other seemed to seal against the Analog Stick and kept the air out, conforming to the convex shape. This is a very minor issue, as both of them will stay convex for at least a while after pushing down on the stick, but I felt it was worth mentioning as a difference between the fit on these two controllers. As a side note, I can't really comment on how the Grip-It would or wouldn't fit third party controllers on the market. If you have access to an original controller and the Analog Sticks on your third party controller appear to be exactly the same shape and size as the PS3 or Xbox 360 controllers' Analog Sticks, then there's a good chance it will fit and, at the low price of around $5 USD, it's worth giving it a shot.
All-in-all, the Grip-Its go on without too much trouble, stay on without any fear of accidentally coming off, remove easily enough when you want to re-center them or take them to another controller, and provide a more "sticky" grip without the introduction of any adhesive or residue that could be implied by the word "sticky." If you're looking to reduce the chance of your thumbs slipping off the Analog Stick on your OEM PS3 or Xbox 360 gamepad, then Grip-It is just what you've been looking for.