The "darkness" was excellent. Good Archer development. I like Archer best when he is making dubious ethical choices in Season 3, suddenly he's very interesting. The contrast from the upstanding and idealistic explorer in the first two seasons is great stuff.. and I think in season 4 we see an evolved Archer.
Absolutely. I like Archer much better in seasons 3 and 4 than I did in previously. I think it gave his character serious depth.