I try not to watch trailers and previews of my favorite shows - esp a show like Dexter - but I've been hearing to much about the trailers I had to cave. Wow! I can't wait for the new season to start!
Sadly we don't know anyone else who watches this show. No one we know gets Showtime and no one are the types to rent tv seasons (even ones which last only 12 hours). I really hate not being able to share something like this. Without seeing S4 I don't think the trailers have the same impact.
Over on the S4 thread I think there was someone who claimed they were giving up on the show because there's no where for it to go. I think these trailers show there's a lot of story left in the series.