I like the idea of Set Adrift mainboard actually because it gives me a bit more confidence about playing into an unknown deck without any counter magic in my opening hand. There's nothing worse than seeing a ancient tomb into T1 chalice resolve and knowing you can do absolutely nothing about it. And anything that can work around that and counterbalance or any other annoying card on the board is definitely worth thinking about. Reality shift also seems like a decent siderboard card, maybe better than vapor snag actually as again it is easier to get around counterbalance, chalice, prelate etc... and deals with its target permanently.
What are people's thoughts on those game 1 hands? I am always agonising over whether I should aggressively mull for countermagic, even when I've got an otherwise amazing hand.