OS X, for the following reasons: Final Cut Pro, Shake, Motion, Soundtrack Pro, Color, DVD Studio Pro, Cinema Tools, Compressor, Logic Pro, Main Stage, Studio Instruments, Studio Effects, Aperture, GarageBand, Pages, Keynote, Numbers, NeoOffice, iPhoto, iChat, iWeb, iCal, iMovie, iDVD, iSync, EyeTV, TextMate,
NodeBox, Toast, HighDesign, Pixelmator, Acorn, Iris, WireTap Studio, QuickSilver, ...