DoubleCommand is "software for Mac OS X (a kernel extension) that lets you remap keys, in other words change the way your keyboard works." The lesson I learned from DC is that badly-written kernel extensions lead to many kernel panics. Here are the painful highlights.
- The machine would rarely shut down or restart properly. Almost every time my Mac's screen would go dark and be unresponsive to keyboard input I could still hear the fan running. The only solution was to hold down the power button to force it off, then get that nasty "your Mac did not shut down cleanly" error message on startup.
- Random kernel panics while plugging or unplugging USB keyboard / mouse from the machine. Very nasty.
- The UI is in no way intuitive and that's putting it nicely. For something as simple as remapping keys, this should not be something you have to fight with.
Stay away from this one. It ain't worth it. :)