The card does have some big flavor implications (for example, being able to attack twice with two weapons in a turn)
I find the Bracket system highly useful for initiating Rule 0 conversations and getting a better sense of what everybody wants to play, especially considering that EDH deckbuilding sites like Moxfield and Archidekt automatically assign an estimated Bracket based on the cards in your deck
Millstone would have a huge impact on one other Magic player
However, he's probably most useful as a voltron commander counter thanks to his activated ability, which can remove important keywords from opposing permanents
It cant attack unless you have one or fewer cards but in Hazoret decks this is almost never a downside, since most of the time youve already used your cards
Cranial Plating converts extra Food tokens and any other artifacts you have into more trample damage, and good ol Blackblade Reforged does the same with the number of lands you control