I've tried my hand at this with coral. I like it, and it works well when you do it right. Problem is stuff that moves (Coral polyps), even with the breeze then it can get tricky stacking.
This is an example of a photo you would like to stack. See the blurry branches out in front as well as shooting off in the background? With focus stacking you could eliminate that and get it all in focus in one image.
Here are the few I did. Obviously was my first time doing it and I missed a few focus points, but overall not much of the frags are blurry where normally they would be. Cool thing is, if I didn't tell you, you probably would of never known.