Think of the things it doesn't affect. Player health, player poison, permanents, quanta, deck.
- If your opponent just got his field set up, you could use this to get in a little more damage before his creatures start ticking away.
- Bring back that Silurian Dragon your opponent killed with Lightning. (he doesn't get the Lightning card back, since you targeted yourself!)
- Thorn Carapace getting in your way? Let your creatures live a couple turns longer.
- In a Time-Aether deck, use it as a pseudo-Fractal for Immortals.
- Duplicate your Hourglasses.
- Return a used spell to your hand - especially effective with Quintessence.
- Use in combo with Precognition or Golden Nymph to time this spell to destroy one of your opponent's important cards the turn after they draw it.
- Get back a card you discarded recently.
- Make a GotP-Nightmare combo even more deadly by casting this two turns after you see your opponent discard a GotP.
This card's principle is very simple - it's a "let's see that play again" card, with certain limitations. I started out with the concept of reverting one side of the field, then realized I had to add the hand-reversion factor in, or it would be capable of massive creature destruction against, say, a Fractal deck or PSNbow rush. I considered adding other things in, but this seems to have the most flexibility strategy-wise, of the options I considered.