And unstable gas would not be a good counter, because before you can play 3 of these you would be dead. Lobotomize would be way better (cheaper and quicker), just remove deja vu's ability to copy itself, remove momentum, remove adrenaline ;P
And you can easily add it in water/aether rush decks (fractal crawlers/puffers/dragons anyone?)
Though I also had an idea some time ago to make a deja vu/momentum/adrenaline deck and the only reason I did not make it is because I don't have elite deja vus.