The first had a good story, the second is almost unwatchable from the shaky cam, the third pulled the trilogy out reasonably well. I thought the offshoot was a cool idea to expand the world and I like Jeremy...he's just too small to be a leading man...he made Tom Cruise look like a big guy in Mission Impossible. Also, Rachel Weiss did something f'd up to her face before the movie and its really distracting.
I'll watch the fifth installment but it's hard to imagine any new ground they can break with the character...and the moon-faced blond handler chick from 1 and 3 being in it doesn't help.