The MTG Salvation Eventide Spoiler just picked up ten new cards from Mana Rouge, including this one:
My first-glance response was "One-mana discard!"
Then I, you know, read it. One-mana untargeted discard means that you're just trading a card from your hand to peel the worst card from their hand. That's not intrinsically exciting, although similar cards have see use in discard-heavy decks such as the recent TarmoRack.
The keyword ability adds something interesting, though. Retrace lets you toss a card in hand, pay the spell's normal cost, and replay it. At first, I thought to myself, "Oh, it's Flashback with a card cost." Then a realized that you can do this over and over again. Suddenly, Raven's Crime might not suck. It's still untargeted, which is not the most exciting thing ever, but if you're playing a deck that doesn't need to stretch its mana base out to get things done in the last game, it lets you just convert all those dead late-game land draws into something actually useful.
I'll be on the lookout for other Retrace cards in the coming previews. So far, we have this one and Call the Skybreaker, a blue-red hybrid spell that generates 5/5 flyers. I must admit I'm still more excited about Raven's Crime, and the possibility of a late-game machine-gunning of your opponent's hand once you've drawn all the lands you need.