I haven't been watching any of the playthroughs at all yet. I've seen enough to know that I want to play it, and then I have been avoiding anything at all besides written articles.
Once it is released, I might check out a few what if I did this sort of thing, but an actual stream, probably not. I got the game. I can play it if I want to see the game?
Side Note: Snape kills Dumbledore
Funny story...my brother spoiled that bit there for me But the story was still good even knowing it'll happen. Which is my point really. If the game/story is ruined with a spoiler, then it wasn't very good to begin with.
But I'm with you. The most I'll do is look up something if I'm confused or curious about something, but I probably won't go anywhere near a video for awhile. Articles and forums like this are pretty good about hiding spoilers.