Not special, just no need to be scared of M4.
Butcher for over 20 years and know my steels and M4 is my steel of choice even though I live tropical. A little extra care needed but still not as fragile as is made out sometimes
Same as the peel ply mentioned in this thread also, never had a issue with it. But somehow it gets a bad wrap. ( remember the uproar when it was first announced on the GB1 )
Another thread it was voted most favoured over full CF last I looked a few days ago.