In some cases we've been building tools that are specific to Linux for the desktop, and they only work on Linux, but I see two major projects that are wildly, wildly successful: Mozilla and OpenOffice, and those two programs are cross platform.
“Never continue in a job you don't enjoy. If you're happy in what you're doing, you'll like yourself, you'll have inner peace. And if you have that, along with physical health, you will have had more success than you could possibly have imagined.”