Hi...i am a new user here. I see all this back-and forth about wireless triggers, and I see them used a lot in instructional videos. Is it personal preference over having a flash unit in the hot shoe that is a fully-functional master? I have a 580EX II (Canon) that I use to control everything. In my view, having that available as a fill I think is pretty good. What am I missing? Am I going about off-camera lighting incorrectly? Is it the cost? I picked up a 580 in fantastic condition for $230 on EBay, which from what I could tell was a great price.