Adobe Creative Suite
Until I can run Photoshop and Illustrator natively, Linux will not be anything more than a hobby for me. Yes there are alternative programs out there such as GIMP and inkscape that could substitute in extremis, but the fact is when it comes to design work Adobe Creative Suite is the one and only game going anymore. If Adobe released a version of Creative Suite for Linux I'd switch over in a heartbeat. But as it stands, my iPhone, iPad and Mac Mini all integrate seamlessly, and even though I occasionally chafe under certain restrictions (please Apple let me set a different default browser in iOS), I have far fewer headaches now than I ever did working in a Windows environment.