I also noticed a lot of people who complained about it being canned before its time where the same people complaining the show lost its direction.
I think the jokes have gotten more adult, but I thinkl thats only for the uncut DVD releases. Hearing Peter say "F***** you" in Stewie the untold story was one of the best moments in the show's history. Of course, later, in the third part of the movie, they used it way too much, due in part to Chris's fiance or wife or whatever she was.
I think the best seasons of the rebirth were the first 2. They were pretty on par with the ones they aired before it got cancelled. The very latest episode seems to want to get back to its roots.
I always wondered what would have happened if the Life with Larry cartoon became the show. The one that aired on CN, when it was just a guy and his dog.