A while back, I wound up reviewing a controller modification called Geltabz; they were an interesting concept, a set of rubberized grips that could be added to a controller's thumbsticks for better feel and control. Bespoke Solutions have come up with their own version, which improves the product a bit;
Like the previous product, Caps4Stix slip over the existing thumbstick heads; fortunately for gamers, Caps4Stix are designed a bit better in the application department, and so the "cut into your sticks" application method for Playstation2/3 sticks is noticeably missing. The basic application process: "invert" the caps, press to the head of the stick, and let the rubber edging flip back around to hold it in place. The trick is getting them lined up properly; with eight hard "nubs" (one for each of the standard 8 joystick directions), it'll feel peculiar if they're misaligned. The rubber holds well, grabbing tightly to both Xbox360 and Playstation controllers. It actually holds a bit better on the Playstation controllers, which have more of a rubber coating to work with.
Caps4Stix come in just one color, rather than the previous product's neon assortment: black. If you're looking to be stylish, you're out of luck, but they blend in pretty well with the Playstation color scheme and don't look all that bad on the Xbox360 controller. The effect's a bit jarring on a Wii thumbstick, unless you're one of those people with all sorts of weird-colored jackets and stickers on your Wiimote to start with. The black rubber also made photographing a bit difficult; three different attempts are above.
Testing this time around consisted of ~160 hours of gaming, with whatever game was avialable at the time. One of the sticks also got an extra "stress test" courtesy of one of the mascots - it was removed from the controller and found in another room, apparently having been batted and chewed. After the stress test period, the "abused" cap had lost three of its nubs and wasn't holding very well (though I couldn't visually find any tears in the surface); the other three were still performing just fine.
The "feel" of the Caps4Stix is a bit different; the 8 directional nubs are quite large, and can rub on the thumb after a while. I found myself taking a break every now and then; a couple of concentric rings, or some smaller but more numerous nubs, might have served better.
Definitely worth the investment;I recommend buying one set to see if you like them, and laying in a couple replacements if you decide you do. If you've small children/pets, look into a more "secure" place to store the controllers out of reach when not in use if you're putting these on.