I absolutely love the age of invisibility thing -
Converse to other posters it has increased my confidence no end.
I always knew that the comments, beeps, shouts, following, you know the harrassment stuff, even the looks up and down which are too obvious and start when you're so young, I knew that I hated it but I didn't realise how much it impacted me day to day till it stopped. And god it's lovely.
My DH once said I beeped and you didn't turn round why not? Because I learnt not to react when a car beeps when I was about 14. After a good couple years of experience teaching me that turning to a beeping car (instinct) was not a good thing to do.
Now, I have no concern about beeping cars, I can stand on the tube without men staring at my body. I have no fear of comments, being followed. Yes it could happen, but it's been so long since it did I have relaxed.
It is brilliant and I love it 
Also has coincided with my career taking off, I think men see me more as a person now that I am older. Which has really helped.
I understand that other women miss it. IME though there's a range from "flattering" to "fucking terrifying" and for that reason most women are ambivalent about it. I would have ditched the former as a young woman if it meant none of the latter, in a heartbeat 