Honestly, I tried Linux on the desktop (a whole other thread, I know), and I, overall, don't like it for desktop purposes. Servers its great
Back on topic:
I use either TextPad or EditPad 2. Both have unique functions that make them nice.
Yes, Im a MS junkie, so MS Studio and Studio.NET is where I spend alot of my time. But for PHP (when I need it) I use a "free" version of Zend.