In the past I used alot of post work in my images but I rarely do anymore, especially now that I have the waterfall/alpha plane deal figured out. I don't think you should break your back just to fake an effect that can be done with a few clicks in post work as opposed to adjusting tons of things in vue. When you have been rendering a picture for hours and hours, then find 1 or 2 little mistakes that can easily be fixed just by using the stamp tool in PS, I say go for it. RR doesn't require you to say if you've done any post work so it can be your little secret.