1. DirectInput is deprecated (http://en.wikipedia.org/wiki/DirectInput). Specifically, Microsoft recommends using regular windows messages for keyboard and mouse input.
2. Not using DirectInput enable us to use the Raw Input JInput plugin to access multiple mice (and keyboards).
3. We're already using windows messages for features DirectInput never supported, so by removing DirectInput dependency, we get rid of some special case code.
4. When we're only using windows messages for input, we're (theoretically) more compatible than with a dependency on a properly working DirectInput.