Spoilers matter to me.
However, generally not in the sense of ruining my enjoyment, but in altering it. Instead of "I wonder what happens next?" it's more of a "How do we get there?" Both of those can be fun.
It heavily depends on what I'm watching/reading, or in what mood I am.
As someone said: Sports! If it's a close and/or important game, I might get really nervous, experiencing a mix of happiness/worry or a mix of disappointment/hopefulness during the game for example.
If I know the outcome? The game often has to be of high quality throughout so I won't just watch the highlights, it's a completely different experience. Then again, sometimes I don't want that feeling of nervousness and watch a game later, reading a spoiler behorehand.
Sometimes I'll read spoilers (plot summaries) about a book or TV series to gauge whether I'd be interested at all. In some cases, that leads me to read the book, sometimes, I decide to skip it. In a few cases I think, yeah, that would've been a nice book to read, but now knowing all this stuff, I don't really care to anymore.