AP Yi has incredible potential. If you can snowball hard enough, you can two-shot people with the right timing. His early game is all about farming. You must farm constantly, just nonstop farming until mid to late game when AP Yi is most effective. His cleanup power is extremely high - get your teammates to get the enemies low and you take over. Zhonya's combined with meditate makes you virtually invincible against non-hard CC. Zhonya's is great for AP Yi because it gives him that few seconds for his Q to cool down.

Master Yi is almost invincible with Meditate and Zhonya's. He essentially has two lives - three with GA. If someone can't one shot you with their burst, you're fine.