Well I wasn't going to say this, since I'm new on these boards, but I have to agree 100% with Tank on this.
And KathyM too. Although I don't believe Superman would have ever had casual sex with Lois, or anyone for that matter, especially as he was her friend and confidante in real life.
Not to mention Lois' part. I have to go with my earlier comment in part one about that kiss.
I agree that the take here on these two has gone completely out of character.
Usually, anyone who loses someone they love, in particular, becomes less likely to be involved in spurious relationships, becomes despondent out of grief, holds on to the memories of the other person as if they were still alive, and holds on to the memories for a long time.
The love triangle in this case is only valid in Lois' case. There are two individuals, as far as she is concerned, Clark and Superman.
Lois "loves" Superman, although he is merely an escape for her, the image of the perfect man, Superman gives mixed signals about Lois, because he is really Clark, and Clark loves Lois.
After Lois realizes she truly loves Clark, the situation becomes a less confusing. more focused, more filled with angst. The S1 finale is a perfect example of that, and the "love triangle" resolution.
To have Lois Lane, sleep with Superman after the death of Clark, her best friend, whom she loved/loves, while not even being through a grieving process is unexplainable.
This has been a terrific TOGOM angle, before the kiss, which I suspect was an intention from the start, but you can only invent new scenarios in which character can be simulated, not invent character actions that ultimately become uncharacteristic, and hope to explain those by circumstances.
It just can't be done. Phew, sorry for the extra long paragraphs.