I'm a PHP developer and now I use Notepad++ for code editing, but lately I've been searching for an IDE to ease my work.
I've looked into Eclipse, Aptana Studio and several others, but I'm not really decided, they all look nice enough but a bit complicated. I'm sure it'll all get easy once I get used to it, but I don't want to waste my time.
This is what I'm looking for:
Are you sure you're looking for an IDE? The features you're describing, along with the impression of being too complicated that you got from e.g. Aptana, suggest that perhaps all you really want is a good editor with syntax highlighting and integration with some common workflow tools. For this, there are tons of options.
I've used jEdit on several platforms successfully, and that alone puts it above most of the rest (many of the IDEs are cross-platform too, but Aptana and anything Eclipse-based is going to be pretty heavy-weight, if full-featured). jEdit has ready-made plugins for everything on your list, and syntax highlighting for a wide range of languages. You can also bring up a shell in the bottom of your window, invoke scripts from within the editor, and so forth. It's not perfect (the UI is better than most Java UIs, but not perfect yet I don't think), but I've had good luck with it, and it'll be a hell of a lot simpler than Aptana/Eclipse.
That said, I do like Aptana quite a bit for web development, it does a lot of the grunt work for you once you're over the learning curve.
For PHP I would recommend PhpStorm.
But if you need Ruby you can try another IDE - RubyMine with same capabilities but for Ruby.