I had to see Paranormal Activity because I'm a fan of anything paranormal.
I seemed like the oldest in the theater, and I'm under 50. I would have preferred less talking to the screen, yelling, and texting from the audience.
This is a love-it-or-hate-it movie, and the friend who went with me hated it. It must be said, though, that this person was brought up to not believe in ghosts/demons. I was, and unless you have that inate fear of them this movie won't work for you.
The plot doesn't move at breakneck speed. Still, it provides good scares, in an old-fashioned way. Perhaps, as technology has advanced, we demand a thrill a minute in movies. Personally, I liked that the movie had a leisurely pace and that the suspense built up.