I also just got back from a pre screening.
All of you should know that you should not expect the EXACT same storyline from the games. Like many videogame movie adaptations, it's in the same world, but fitted for the big screen, so not everything is the same. So, without spoilers, I thought the scenery was dead-on, music was just the same (pretty much). There are several really dumb-as-shit lines in it, but they don't ruin the movie. The acting is for the most part, on-par or even above the games at least, but not phenomenal. Of course, you shouldn't expect much from a Silent Hill in terms of acting. The movie has elements from every one of the games, even if very subtle, and it's a nice touch.
**SPOILERS**
I really liked how when she first got into Silent Hill, even the camera movement and angles are just as they are in the original game.
Also, the introduction scenes were garbage
**END SPOILERS**
Overall, I enjoyed it but it really doesn't make my top-anything list and I don't expect to buy it on video, but it was worth the nothing I paid for the tickets. Okay, I'm probably going to see it in theaters again with friends tomorrow, so it's at least worth the price of admission.
I guess that's my two cents from a guy who loves the videogame series.