What struck me during this GR is that, as you point out, Darcy made up his mind about Jane in one evening. (Talk about having confidence in one's own judgement! IMO he beats Elizabeth hands down.) Although he had obviously seen Jane and Bingley together before, it was only Sir William's comment at the Netherfield ball that made him aware that things were more serious than he had realized, and decide to take a closer look.

You're right about his not apologizing for hurting Jane - I thought he had, but all he says is that Elizabeth knows her sister better than he does(!) and that her resentment is "not unreasonable".

I'm not sure if Darcy's criticism of the Bennets' behaviour can be called grasping at straws (by JA's standards), since Elizabeth later takes it quite seriously. However, I agree about the *double* standard: Lady Catherine can be severely lacking in good manners, but not the Bennet family, oh no! I can think of two excuses (though not valid reasons!) for this:

1) Darcy is used to Lady Catherine's bad manners, since he has known her all his life, so he doesn't notice them the way he does the Bennets'.

2) I think Wickham was right when he told Elizabeth in ch.16:

"[Lady Catherine] has the reputation of being remarkably sensible and clever; but I rather believe she derives part of her abilities from her rank and fortune, part from her authoritative manner, and the rest from the pride of her nephew, who chuses that every one connected with him should have an understanding of the first class."

] Col Fitzwilliam was right about affection between the couple lessening the honor of Darcy’s triumph.