Chipp...why do you use the alpha channel with layers instead of the transparency? Is it just your preference or another reason? 

One thing I've noticed using layers and mixes during these recent discussions is that often they wind up in the same place and pretty much look the same in the hierarchy. It's hard to know, for me at this point, when to do a layer mat and when to do a mix and for what desired effects. (besides the cool environmental controls)  Maybe before these threads are done we'll have enough info to formulate some basic guidelines for their use....