I have used Dreamweaver on my PC for many years. I think that it is the best IDE on the market. Why? Because both novice and seasoned web developers can use the same tool. And both will find it beneficial.
That being said, when I began to use my Mac for web development, I did not want to dish out the bucks for Dreamweaver, so I started using Aptana Studio.
I also am a PHP developer, so Aptana Studio’s built in support for PHP was also a consideration. I’ve used this IDE when developing with CakePHP and CodeIgniter.
More recently, I have used Aptana Studio on my Ubuntu box while doing Django development (see my post: Setting Up Ubuntu For Web Development).
So what is your favorite IDE and Why?