I've seen the series and liked it. It's definitely NOT for the faint of heart or queasy of stomach! I do think that while it was a good series, I think that the story line was stretched a little thin over the last movie or two. I'll have to co back and watch them again. At one point they were all on NetFlix but now they only have the last one, on instant at least.
Also, the trailer you linked is from the fourth movie.