This thread is a couple of years old. Since then I've updated my 60mm macro to a 105mm macro (both Nikon).
Makes insects easier than the 60mm. Used to have to be right on top of them. Gives you more options. Just wish I had PS to focus stack.
Ps does a great job with focus stacking but it's not the easiest way to do it especially if you're stacking a ton of macro shots. Give Zerene a try AFB: http://www.zerenesystems.com/
It's quick, easy (automates the whole process), inexpensive and you can download a free trial. I know a macro insect photographer who swears by it for focus stacking 100+ shots into a single image.
~ Peter