I've spent some time playing with photo stacking for macro shots. What I found out is that it gives one an amazing control over the depth of field.
One issue is that some edges are not stacked properly by Photoshop. (aka produces blurry edges). How do you avoid that? (see the zoomed-in version of the multi-layered ring)
What software do you use for photo-stacking?
Did you layer align before layer blending?