Paco is largely obsolete. The dependencies it requires are not available on modern systems (php-gtk2 was discontinued).

Paco's a graphical text editor aimed towards programmers. It has most of the features expected in such a text editor, plus a few extra. The only thing I personally think it's lacking is syntax highlighting, which is the next major planned improvement.

As far as special or notable things about the program, there are a few. For one, it's written entirely in PHP. I believe it may actually be one of the only, if not the first, real desktop application written in PHP. It needs some testing and debugging, as such. I've managed to get it to work fine on my desktop (Slackware 11.0) and my laptop (Gentoo-pcc 2006.1) with PHP compiled as a CLI with POSIX support. The POSIX support, I might add, is not needed. Only one function actually uses it. It's there as a part of future additions. Ideally, it will be removed, making Paco fully cross platform.

In addition to that, Paco includes a feature called double view, which lets you open a text file in two different panes. One pane is an editing pane, while the other is a special viewing pane. The contents of the viewing pane are updated as you type, so it will always show the current state of the file you're editing. So how is it useful? You can scroll through the viewing pane to look at a different part of the same text file you are editing, like if you need to look back at a function you already wrote to see what arguments it takes, or if you need to see what you called some variable or something like that.

Oh, and to use Paco you'll need to have GTK 2.x+ installed, as well as gtksourceview (if you have gnome installed, you have this), and PHP-GTK-2.x (available from gtk.php.net).