iPhone developer Jonathan "Schwa" Wight offers a great little trick for creating pixel perfect glassy buttons: using the unofficial UIGlassButton class in the simulator to build your art. In his code paste, he shows how to build a button and render it to a PNG, which you can then save to your desktop.
It's a great little trick, and one worth adding to your development arsenal. Be aware that UIGlassButton is a private class, and one that has long since been relegated away from the official SDK development path. Although it continues to work on the Simulator, it's not for use on the iPhone itself or in App Store projects.
Continue reading on to find the code. Don't forget to substitute your own user folder into the code (in my case, "ericasadun") for Jonathan's ("schwa").