You have a looooong way to go before the interface is anything remotely resembling cluttered. Have you SEEN Houdini? Or any compositing app, for that matter? ;)

I had an idea on how to fit them into the interface, as well as improve the way they work. Add them in as an option under the line tool. Click the button and you go into guideline edit mode. Add and remove guidelines as you wish. Click DONE to turn guideline mode off. If you want to edit the guidelines or add new ones, just go back into edit mode.

I didn't realize the power of guidelines until I saw a Studio Tools video the other day. Then the genius hit me. Having that kind of ability in MoI would be phenomenal.