I bought a silicon skin for my Sidekick. I had a dark blue hard snap-on skin thing before, but one of the little tabs holding a piece broke off and I thought I'd try one of these to replace it. I'm quite happy with it; it fits fine, the silicon feels cool in a weird way, and I can still use my phone fine. It even still fits in the carrying case, because the case was already stretched out by my old hard skin. Only problem is the part they sent to go around the actual screen really doesn't work at all, but that's easily fixed by using the screen cover from my old one.
I just realized my phone is now blue and kinda magenta...and that makes me absurdly happy, because my phone shares my Phoenix/Miles love. I have no excuse. :(