I used Eclipse PDT, Aptana, Netbeans, and Komodo. For Web development (at least my style: PHP, Python, Perl, HTML, JavaScript, Ruby, CSS, all the goodies) nothing has touched Komodo IDE. There is a free/open source version called Open Komodo that, unfortunately, is not as feature complete as Komodo IDE but still great. It runs ons Windows, Linux, and Mac (which is a plus since I use all three at times), is completely extendible through plugins, has source code repository features, file transfer features (s/ftp, scp, etc) and so much more. What it really wins on is polish (things like multi-language/library code auto complete).