One of the best bounce spells ever printed, efficiently answering cards like Thalia, Guardian of Thraben, Gaddock Teeg, Sphere of Resistance and Leyline of Sanctity. The only downside of this card is that Chalice of the Void on one is very popular, causing this otherwise perfect bounce spell to be not great at times.
A “cool trick” you can do with Chain of Vapor is to use it to generate mana and storm – a pseudo “storm engine” so to speak. When you have a bunch of artifact mana (Chrome Mox, Lotus Petal, and Lion’s Eye Diamond), you can target your own artifact, sacrifice a land, and then copy it. When you have enough lands and artifacts, it can be the cause of your opponent’s demise. I find myself doing this post-Ad Nauseam in scenarios where I’m low on resources. Maybe you needed to cast a few cantrips or discard spells, after that, you can bounce all of your copies of Chrome Mox and replay them and imprint with the extra cards from Ad Nauseam – you’ve created mana with a bounce spell!