I saw Cloverfield with my son yesterday. It's definitely a different take on monster movies, but I enjoyed it quite a bit. It's kind of a vindication for Blair Witch IMO, it's a similar style, but while BW kept you wanting something you would never get, Cloverfield rewards you pretty early on with some nice special effects and sightings of what you came to the theater to see. I also felt pretty immersed in the situation, there were times when I felt like the guy behind the camera, living the situation, trying to outrun something you can't really outrun.
I haven't seen The Host, will make a point of it now tho, I love a good monster movie, and based on what people have said, it sounds like something I could get into.
I don't much care for the "this ripped off that" mentality at all, I think if you can make a quality piece of work, even if it does take pieces from another work, as long as you come into it with your own angle, you can't be faulted for that. In my mind, Cloverfield took pieces from Blair Witch, Godzilla, Alien, and maybe this Host movie, and came out on the other end with something I enjoyed and will see again.
I do think it's pretty amazing that it made $41 million in the opening weekend when 4 out of 5 people I talk to are like "Cloverfield? What's that?"