Basically I've only seen the three 2012 onwards series in full and wondered which of the 2001-2008 series people preferred. Luke asked about BBAU earlier and it just reminded me that I really want to watch an older series in full sometime.
I've seen the early weeks of 5, 6, and 7 but never finished them (not out of boredom because I actually enjoyed them all, I just sort of kept forgetting to finish
).