Only using the Cyclorama when I'm feeling a bit lazy. Really, for the best effect,  I use props for most of my backgrounds (buildings, trees, walls etc) and only leave a small space for the imported sky background. Most of my stuff is urban. Takes a lot of time but I think it looks better unless you really need open expances of terrain like beach or mountains. Terrigan is good for this. It's FREE and simple to use.