Juanjo,
I've switched from windows to macos x, and haven't looked back! The great thing about OS X is that you can open up a terminal, and you have all the power of unix from the command line. Also you can use MS Office on the Mac. Either buy the Mac version, or buy virtual pc and use your pc version.
You'll find a lot of development tools for the Mac. They include JBuilder, emacs, BBEdit, XCode, etc. You should also check out Fink, which is a package management system like apt-get.
If you don't like the one button mouse, then plug in your two button mouse, and you have right click for contextual menus. Or upgrade to Apple's Mighty Mouse for 5 mouse buttons.
My recommendation would be to take that leap of faith and make the switch.
Cheers,
Nick.
