I think the main reason I don't go for *nix is because I'm lured in by all the coolie apps that Windows has. No matter what I want to do, windows has it - somewhere. Because the user/developer base is so much larger (Because thats where the money/consumers are).
I think if *nix had dreamweaver, flash, photoshop & some way to conduct secure IM's (via icq, aim etc) to windows machines, It would be hard to keep me away.
The rest of the stuff I use are pretty common utilities that Xwindows undoubtedly would have replacements for. Ahh the replacements.. thats the other downside to *nix... theres far less choices for the replacement apps.
Another cool thing about *nix is you have FULL CONTROL over whats going in and out of your network. You could argue that you do with windows too, but only if you had a linux router setup as a gateway

-- windows and 99% of it's apps are closed source, many of them like to 'phone home' for one reason or another.
I mean it all boils down to applications VS privacy/security. With windows you'll have applications galore, but you'll sacrifice your privacy and security. With *nix, you might have to give up
luxury versions of various applications or tools, but you'll gain a lot of cool apps and tools as well.
But I aim to switch sooooooooon.
Speaking of "switching"... Apple is also a viable option.. its sort of a little of both. You have the closed source Apple OS stuff (which gives you alot of the cool apps you would lose with PURE *nix -- like adobe/macromedia stuff), then you can run all of the Xwindows and unix stuff as well.. because its built on *bsd anyway. With OSX you can drop to shell and do just about everything you could on a linux or freebsd box.
If your anti-microsoft for some reason but don't want to give up your design apps, go Apple. If your hardcore.. pure *nix (linux, bsd, solaris) is the way
