Its base power and toughness arent amazing, but it does the job
An extra turn might not seem that amazing considering you won't have much mana left the turn you cast this, but the real power is that it gives you the opportunity for all your other creatures and planeswalkers to provide extra value
Past in Flames is a staple in both Modern and Legacy, Cabal Therapy is a Legacy all-star, Conflagrate has finished many a game for Modern Dredge, Ancient Grudge is a sideboard staple, and the list goes on, including Lingering Souls, Roar of the Wurm, Dread Return, Unburial Rites, Desperate Ravings, Deep Analysis, and Faithless Looting
Being able to return creatures to the battlefield each turn, even in lieu of haste, is going to ruin a lot of opponents days
The game offers a premium subscription and in-game currency, but my early sense is that theres plenty to do for free, too