I stopped watching it, to be frank, found it not attracting me anymore since the highlight of michelle in S3, it just became a bit... far fetched, and over the top. It went on to be that HIT SHOW instead of that little title of whom the producers were actually to scared to release, because the main audience could easily find it too heavy.
so, for me, it went like this:
season 1: GREAT
season 2: FUCKING EPIC
season 3 (first 4 episodes):... giving it all they got, now they know that they have put up a fanbase.
it's a bit like the saw series to me, it's fun when they try to find the lines they can/cannot cross, but when they know it, they just go all out, knowing they don't have to fear anything anymore.
so, for me, you can spoil it :P not sure about nan though :P