Is it a good thing for you, or does it tend to ruin things?
With the exception of movies, it always makes it a more enjoyable experience for me. Especially for games. I like to go into heavily anticipated games like OMG THIS IS GOING TO BE THE BEST THING EVAAR and get as excited about it as possible. It makes flaws so much easier to ignore, and sometimes I even find them endearing when I really shouldn't.
With movies it just leaves me a tad disappointed when it doesn't live up to my expectations xD
Of course this isn't true with horror films. If someone tells me a horror movie is the scariest thing they've ever seen, I will be scared when I watch it. Like, OH MY GOD IT'S A SHEET WITH HOLES IN IT GHOSTS ARE SCARY ;_;!!!