Mac
We have been developing Mac OS X with Cocoa applications since 1992, and we master the tools and techniques required to build excellent Mac OS X software. This expertise has been used in public (Goban, GPGMail) as well as private (Animotion) projects. OCUnit, our automatic testing framework has been integrated by Apple into XCode, a component of the Mac OS X development tool chain.
Windows
We wrote or ported several Windows application, using diverse development environment. Our favorite environment is currently Qt. We also frequently use Windows during the development of embedded systems.
Linux
We also prefer Qt to develop on Linux and other Unix flavors.