Does anyone use outdoor cat runs?

Our three furbabies are inside only, and I wont allow them outside unless they are on a leash - for their own safety. I can't imagine having anything happen to them.

We've got a smaller run that they just adore, but fight for the sunny spots. We're looking to extend their run along the whole length of the house - kind of like an add on.

Does anyone have any experience in building cat runs?
I'd love to see some photos if people have them, for ideas