I have seen all of them, went to the ODEON to watch SAW IV last friday on its release night, top film as of all the others but it left me really really confused, and so much so that i have started to rent them all again from the begining to see if it sheds any light on things!!!
Ive seen I & II but i'd seen enough of them by that point to not bother with the others! Decent films mind, but too much of a good thing in my opinion!