^^ Yeah I've noticed that women are less likey to thank me for letting them out BUT the ones that do say thinms tent to make a beigger deal out of it!
Like with a guy you get a hand raise - which is enough. But with girls I seem to get a hand raise a big smile and a mouthed "thank you" - as you pointed out though, that's on the rare occasions they bother to acknowledge at all! It really pissed me off when people don't acknowledge

I actually went though a phase of blowing kisses at girls who let me out or what ever - it normally seemed to make 'em smile, maybe I should bring that back!