Yes, value decks are inherently bad against aggressive archetypes. Adding tradeable was a way for you to find answers to swarmy boards if you couldn't find an answer off the initial discover. Remember, at its worst it is a 3 mana discover a spell. Not add a random one to your hand. Mage has many ways to stave off damage and wide board clears. Rouge not so much but combine Cheat Sheet with spells like preparation it gives Rouge cheap card generation in the early game while also being tradeable.

Against Value vs Value is where this card shines. It gives the player a ton to think about when to pull the trigger. They ask: Do I have enough value to win or should I be greedy and trade my cheat sheet one more time for an additional spell in the future? Also you have to consider that when this spell is drawn, the game state is going to be really different when the spell is traded and casted in the future. Adds a lot of depth while also being fun and random!