I love the interplay between background, alignment, current behavior and future behavior. The characters are well-fleshed out and their alignments are appropriate for their backgrounds and fit their likely future actions as well.
Alignment and action should influence and reinforce each other, so its important to choose an alignment that you can stick with.

But alignment is not personality. You can be a good jerk or evil, but generous. That's why it hard to balance the motive/action conflict other's are talking about. You have to determine the perspective of the being judging alignment. For example the LG god the two characters worship and a CE god would have different perspectives. I'm not saying alignment is relative, but the LG god will have a different idea of what makes something good than the CE god, becuase they are influenced by their alignments. The LG god may think that a good motive is good enough (because he looks at the heart) and the CE god looks at the results (because he just wants more dead people).

What's worse is if the judge is not omniscient enough to know both motive and action. If the god of the paladin who mistakenly kills the innocent villagers is not omniscient he may not know the villagers are innocent. He may not know his paladin thought he was doing the right thing.

Usually, however the judge is the DM. The DM is omniscient (at least in the game) and does not have an alignment bias. But the DM does have a personality and moral compass of her own. She may be a Puritanical teetotaler or a godless heathen and that will influence how she judges alignment in the game. It really doesn't matter how the books try to suggest alignements, the DMs moral compass is usually pretty set. As Solaris said

"That said, there are very, very few things which will excuse genocide. Very few. None of them happen in the real world."

In her game, that's an absolute.

Detecting evil- I think the subject has to have an aura and only those classes with auras are detected. I believe there's a typo in the spell description where it refers to the presence or absence evil and it should say auras (see Detect Magic). Also, the chart refers to creatures with certain HD and PCs don't have HD they have levels.