I seriously looked at the Macho Man Disc a couple years ago when I needed a new all-round and commuting bike. I didn't end up with one because of the aggressive head tube length/stack, but now I'm starting to look for a more dedicated gravel bike to drop some weight from my Tamland. The Cosmic Stallion will definitely be on my short list of considerations, along with the Gunnar Hyper-XX since I like my Roadie so much.
As for the brake mounts, I think it makes sense that they went with post for the frame/fork. It allows people to use brakes that they already own when building up a frame, but still allows for the new flat mount standard. The way I understand it, flat mount brakes can be adapted to post mount frames/forks, but post mount brakes cannot be adapted to work with flat mount frames/forks.