The Witch's Brew — would you have taken the bargain?

Vesper offers Ethan a choice, and one night to make it. I've heard from a few readers who were sure they'd take it, and a few who were sure they wouldn't, and interestingly they don't split the way you'd expect.

So: take the bargain or walk out of the shop? And do you think Vesper already knows what you'd choose?