I hated Season 3 at the time, but I re-watched it and liked it a lot more the second time around. On the flip side, I really loved Season 2 the first time around and did not like it as much as I remembered. There is a huge gap in quality between 1-4 and 5/6 for me.
1 > 4 > 2 > 3 > 5 > 6. Right now, this season is up there with the best for me.