Works fairly well. Although at larger vert counts this takes forever. I tried it on Suzanne, subdivided once (that's only 3700 edges) and it took nearly a minute. I wonder if there is any way to speed up the script.

Thanks for testing! I was unaware of that speed issue, I'll have a look at it, maybe I can optimize something...

A question and a suggestion:
- What does this script offer, that blender's built-in command doesn't do (ctrl+alt+shift+m)?
- Currently you're iterating over all faces for each individual edge, which gets very slow for large meshes. Perhaps it's a better idea to iterate over all faces once, and create a dictionary with for each edge the number of faces it's in. That way you get the same result with only one iteration over the faces, instead of 'total-amount-of-edges' iterations.

Good luck,
Bart

Bart you got me... I'm very ashamed to confess that until today I didn't know that built-in command (it's even written inside the menu, what a shame :) )
I guess my script has become instantly obsolete, which is good, much better to have a built-in command.
I think the best thing to do is to close this topic? I think I cannot do it myself, some of you would be kind enough to do it? Thanks!
Yorik

I had not realized there was a command in Blender either.. oh well, you learn something new every day! It was a good script, although the built-in one is much faster ;) Hopefully you'll be able to come up with some other good ones.

I've closed this for now.