Linux

It took me a while to finally break down and install Eclipse and actually use it for Drupal development. In my mind it was one of those daunting tasks that I never thought I'd complete. Once you start using it for real, though, it feels like you finally got the Swiss Army knife you've always wanted, but now it's too big to fit in your pocket.

I am a happy Linux user. I have been using different flavors of Linux for almost a decade now, and haven't seen Windows since the days of XP Service Pack 1. All my coworkers use Apple products (am I the only web developer that has never owned an Apple product, ever?)

I eventually settled on Ubuntu for desktop use, although my web server runs CentOS.

In any case, I swear by vi. And for most tasks, it's all I need for Drupal module development.