Heres what I do....

for HTML and CSS, I use Dreamweaver (didnt pay for it :/). The suggestions have completely spoiled me.

For learning a language, I use Notepad++, because it helps a little with the syntax (not too much), helps you stay organized, and doesn't spoil you.

Full blown sites: Zend Studio
I don't even know what an IDE is, I just like it's medium weight interface and its project management capabilities.

I will look into phpdesigner and Eclipse, I think every software should be tried before it is decided on what your favorite is.

Edit: after looking at the software, it comes down to PHPDESIGNER or Zend Studio for the top... At least in my eyes.