This is most probably yet another form of wasting time, but for some time I have wanted to have all main varieties of operating systems available in a single workstation. There is some benefit in this (e.g. comparing the performance and usability issues on identical system), but mostly I have been playing with the system just for the fun of it. Tonight I finally got Mac OS X Leopard (using the “Leo4Allv3” hackintosh installation), Ubuntu 8.04 LTS and Microsoft Vista living side-by-side in one sweet multiboot harmony, hooray:
frans goes blog 
Well, which do you prefer today as a general-purpose OS? I use Kubuntu, Leopard, Windows 2000 Pro and Vista Home Premium on different computers and I’m still not sure which I actually prefer. It’s certainly not Vista, which is a nasty resource-hog and likes to do all kinds of crap behind your back to “help” you. Unfortunately it’s not Linux either. Every now and then you still have to do a bit too much manual tweaking to get it running. And the newer distros with lotsa eye-candy (like Kubuntu) aren’t very light either with regard to CPU cycles. Win 2k has more or less lost all support so good luck finding drivers for your new hardware etc. Leopard 10.5.4 comes close to the top, but still after nearly a year I have difficulties in understanding its functionality and mentality.
I actually think the OS question comes to a draw between OS X and the one I don’t currently have at all: a well tweaked and mature Windows XP!
I do not actually find so much real use for OSX — there are great graphics programs for it, of course, but I am not a graphics professional so I have kept with those tools that come with the package. Windows is the most genuinely useful OS when it comes to real world use, and that is not so much a feature of the OS itself, as it is related to how various devices have their driver support primarily (or only) for Windows, and the common-user application space is so much more extensive for Windows. Said that, there are e.g. server application style tasks where Linux is my preferred system. I guess OSX comes last in this comparison.