Interesting plugin :) I am not using it yet but I have a question:
Because I am already running another jquery lightbox thing (Easy FancyBox) on my site, I would prefer to not load colobox at the same time.
I can hack colorbox out (I suppose) but it might be a nice idea to make it configurable. Like an option to either use the integrated colorbox or an external one: in my case fancybox.
Is this feasible at all? If so, I'm available for some testing and aid with necessary code...