Mac

I bought a Macbook last November because I want to have a machine solely for programming and works, Windows is mainly for video games purposes for me.
I’ve been using Mac for a couple of months, I think it got the best worlds from both Windows and Linux:

• A good GUI
• No need to worry about hardware driver issues (For me this is the main reason why I gave up installing Linux on my laptop)
• Unix based bash tools
• I’m more comfortable to mess around $PATH and install programs globally, compare to Windows
• single OS & Hardware environment makes me easier to Google my questions

Of course it’s not perfect, there aren’t many choices in terms of accessories, you pretty much need to stick with Apple branded stuffs and they are just expensive.
And regular mouses just don’t work well with Mac OSX.