Chain of Vapor is better than Shattering Spree against aggro, and Shattering Spree is better than Chain of Vapor against aggro-control. Considering that the deck needs a substitute for Xantid Swarm against aggro-control, I think Chain of Vapor should be used instead of Shattering Spree, because Chain of Vapor is always atleast a Time Walk, while Shattering Spree is often dead.

The combo elements of Chain of Vapor do work well in this deck, all Chain of Vapor needs is 2 artifacts and 2 land in order to generate a significant storm count, and it's not difficult to generate additional mana off of a Chrome Mox or a Thresholded Cabal Ritual.

I still advocate using 3 ETW main, I win more games with ETW than I do with Tendrils against the most difficult match ups, and other people SB in ETW against EVERY match up, so what's the point of wasting SB space on it?

One change I have been testing is replacing Brainstorm with Night's Whispers, while it slows the deck down in comparison to Brainstorm, it imprints for black mana, digs deeper (2 cards plus two draws as opposed to 3 cards and two dead draws) and it generates card advantage (and in turn card advantage creates Threshold). The deck has to be more aggressive with Chrome Mox and Lotus Petal, but the additional card makes up for the loss of storm.