I'd rephrase that to be– do you work in a team with uncommonly high standards? I'd imagine this to be the case at any cutting-edge company. Consider say, the special forces in any military. If you don't meet the grade, or you don't carry your fair share of the weight, you don't get to stay. That's just tha name of the game. I assume that this must be the case at all the exciting companies– Tesla, Google, Apple, Facebook, etc etc.
It's not stressful if the expectations are set in advance, and the precise conditions for firing are clearly stated, and you get the feedback and assistance you need to stay afloat.
I work with a small team that prides itself on being results-oriented, and I love it. As far as I can tell, everybody we hired is hired because they bring their A game.
I'd much prefer this to being a part of a team that "carries" people who don't perform.
Of course, we've all also heard horror stories by now of ridiculous young founders who come up with extreme ideas about productivity, 80-100 hour work weeks and whatnot. Sustainability is important.