It's an excellent source of card advantage in your manabase if you're playing at most one, maybe two colors, and it can fill in gaps for colors that don't have unmitigated access to card draw
This means that, even if you have seven cards in your graveyard when you first cast the spell, if you lose cards from your graveyard before it has resolved on the stack, like through paying escape costs or a well-timed Tormods Crypt, you could fail to meet the threshold by the time it resolves
5 Coat Of Arms Rats Are Stronger Together If you have a ton of creatures with the same type, Coat of Arms is amazing
First up, its an enchantment, so it can be interacted with with twice the amount of removal spells
With only one power, it seems hard to blow opponents out by flashing it in after attacks, but it might be a sideboard all-star against aggressive decks that rely on one-toughness creatures