This card is actually fairly underpowered compared to the other options out there (most notably Undying Evil and Cauldron Haze). It is also available in "seal" form with Angelic Renewal and (repeatable) aura form with Gift of Immortality. The main advantage this has over all the other revives is that it is the only repeatable one (no counter interactions) that fits on a stick (unlike the more powerful effects, like Second Sunrise and Faith's Reward).

@RiftenBlack
You missed that this specifies "owner's control". Grim Return can be used to steal an enemy creature after killing it with something like Doom Blade, which makes it almost a black False Demise.
@Adunar
This triggers on death and puts it under its owners control. The Treacherous Pit... (see all)