This card looks fun. In a blink deck, you probably have a creature with an ETB effect lying around by turn 4, and can flash this in at the end of turn 4 and exile it. The horse has no evasion, so the opponent can just trade with it in combat, but then you triggered the ETB of whatever you exiled twice and traded for a creature, which is a 3-for-1. If you exile a Man-O-War effect like Barrin, Tolarian Archmage or a creature with ETB removal like Skyclave Apparition, it's likely your opponent won't even be able to trade, and you set them very far behind on tempo.
Most of the time, the floor is a 4/3 flash for 4, though it can be even worse if you only have creatures you don't want to exile, like mana dorks.
However, the card is blue, which means it is not for powered cubes. Larger unpowered cubes with a strong blink theme might be interested. I purposefully overvalue cards with flash because combat tricks make games more interesting, so I am excited for this one
To be honest this is the first card in either AFR set that makes me somewhat excited to give it a try. As mblieb says Steed is pretty broken with the new 'free' evoke creatures like Solitude, Grief and Fury, but it looks plenty powerful in its 'fair' mode with some random creature with an ETB trigger (plenty of those in cube). Going to give this a shot.