I'm probably late to the party on this, but goddamn does it make DOOM just that much more fun. Plus it adds a couple new bells and whistles.
I seem to recall the mod author being some sort of asshole with dubious politics, but I guess that's not surprising considering the content. It's a free mod though so it's not like you're giving him money and the gorey splattery action is fun :shrug-outta-hecks:
There's a video essay about him as the first result when you look this up. I almost don't want to know. Let me have my fun haha.
you can also check out Project Brutality, which is based on Brutal Doom but with even more stuff, and as far as I'm aware doesn't have any notable developer drama going on
be careful installing other mods with brutal doom, otherwise you might get a suprise!
spoiler
there's a couple doom mods that go out of their way to detect the presense of brutal doom and then activate game ruining code if it does
coz like the other commenter said, the creator of brutal doom is a massive poo-poo head
