This movie is everything a horror film is supposed to be: tons of gore, a hot young cast (most of which can't act all that well), and a host of veteran actors (Brad Dourif, Keith David, Betsy Russell, etc) making appearances.
From the title, you have probably gathered a bit about the plot. There is a chain letter targeting a technology-obsessed group of teens. They have to pass it on or a psychopathic killer mangles them in a most creative way.
A combination of "The Ring" and "Stay Alive," this movie avoids the excess torture of the "Saw" films, as well as the long drawn out storylines of other films of this nature. It's just a good time. There is nothing stunning or original about the film that will make it stick in your memory forever, but it satisfies the horror film lover's appetite for lots of gore, a little nudity, and an overall great time.