and I think there can be more than one interpretation. At such an assembly as this could simply mean "at an assembly where I know no one but my own party"--giving him only one reason, rather than two. After all, even if Darcy could guess fairly easily that no one would be his social equal at the ball, would he have known that no one was the Bingleys' equal? He danced with Bingley's sisters, whose father had been in trade. Indeed, I think you have argued elsewhere, Robbin, that Jane was Bingley's social superior. Why did he make an exception for the Bingleys? Because they were his friends!

Also, Darcy never says the men who have neglected Lizzy are inferior to him--you are assuming he meant so, because of what he says and does in later chapters, aren't you? Personally, I have never even thought of interpreting the line that way until this discussion (and I have read P&P probably a dozen times over 20+ years).

By the Lucas's party, Darcy and Lizzy have presumably met at the 4 evenings where Jane and Bingley were getting acquainted (Ch. 6). He also had begun listening in on her conversations. Then they had a lively, if short, exchange about what she had said to Colonel Forster. If Darcy is now ready to talk with her, why would he not be ready to dance with her as well?

I think that he is very reserved, and slow to warm up to new people and situations. I actually believe he began seeing how pretty Lizzy was because he was getting used to her. When she was a total stranger, he could not see beyond her "strangeness" (once again, he was blind). People who have "spirited" children would be familiar with the trait of "negative first reaction" that I see in Darcy.