Which OS.s (operating systems) do You consider a smootly-runnning, good-looking OS to develop artpieces (images, movies, music, games) on it?
Any operating system should be able to meet those requirements with the help of the right hardware vendor. I like Photoshop, After Effects, and Sound Forge running on an Intel motherboard and processor with Windows XP Professional. I also use AVISynth, which is only available for Windows (hence the AVI-ness of the name). Matrox makes nice video hardware, and of course, there's the NewTek VT[3].
Trev
