gistfile1.txt

This comment is going to be extremely biased, but that's just the way I am.

You didn't mention Linux.

For coding, vim is the way to go. It's the best editor out there IMHO.

GIMP/GIMPShop for slicing images. (GIMPShop has a very Photoshop-like UI, or so I've been told. I've never used PS)

Apache and WEBRick for local testing servers. (No real difference there)

Chrome. (Again, not much difference)

git/ssh/svn are also there. (Not much difference here either!).

Also, for Ruby, rvm is a must. The version of Ruby packaged with most Linux distros is insane (To put it politely!)

Things will be "strange" at first if you do switch, but that's what I use. It's also a heckuva lot faster than Windows, for the most part. You can also dual boot Linux and Windows, which means you'll be able to keep Windows (Which you'll need to if you've got an iOS device, and I'd recommend keeping it in any case so you can do IE testing, testing in Chrome Win, etc)

I use Ubuntu (And other flavors of Linux) all the time. I haven't booted into Windows in forever. Also, you'll be deploying to Linux servers for the most part, not Mac or Windows.

Even thought Mac OS X is *NIX based, it still isn't the same as Linux. Mac OS X is BSD-based, and doesn't really work the same way as the Linux Kernel. There are some minor (but tricky) differences.

With that said, it's personal preference, just like what editor you want to use (Be it vim, emacs, TextMate, a full blown IDE etc).