Hee, yes, I empathise somewhat with Arthur (considerably more than with Molly: I have never been in the slightest popular, but I did have a crush on a popular girl when I was at school... bad for the f/f thing as well as clearly not going anywhere!)
I wanted this to be realistic, so the first sex wasn't great, and they had the tough bits... but they're so in love, and it shows in the books, I Think.