I use Aptana whenever I have to edit a web template or convert one to a WordPress theme. Before I found Aptana, I used Dreamweaver. I wrote a post earlier on how to use Dreamweaver to edit edit WordPress themes.
EDITING WITH APTANA. Porting an open source web template into a WordPress theme using Aptana. [...]

Now, what do I do? That was the first thought that formed in my mind when I first opened Gimp about 5 or 6 six years ago in an Internet cafe on F. Ramos St. in Cebu City.
I was given the grand tour on Linux and open source software by Mike Schmeisser, a chain-smoking German [...]