Not too sure on any of the *nixes, I've run a couple, but never done any hardcore fooling around with them (i.e., any sort of network admin). But, by far, the
worst operating "system" (if it can even be called that) was
Microsoft Bob. Not only was it the fore-runner of the evil Clippy, but it also had security holes large enough to drive trucks through (like the "feature" that allowed a user to recreate their password if they typed it incorrectly three times).
