It is even better if they have no cards in play or minions to attack with
Because there's a pretty firm "ceiling" to how powerful removal can get, Wildcards spent this way will let you play with them for a long time
If you gain control of another player's permanent until end of turn and exert it, and then that player regains control of it, it will untap during that player's untap step
Look at this guy with a giant pile of coins and he's biting them
It doesn't copy whether that permanent is tapped or untapped, whether that permanent has any counters on it or any Auras and/or Equipment attached to it, and it doesn't copy any non-copy effects that have changed that permanent's power, toughness, types, color, abilities, or so on
This high percentage means that selling one booster box of Shadows Over Innistrad, Amonkhet, or Hour of Devastation is unprofitable on eBay