I find it funny when people extend on what Harry and Ginny did during that 'happy half-hour' by the lake; I mean it's not like they would have done anything right there, out on the lawn for the giant squid, hagrid and half the school to watch. I really don't think that it needs to even become an issue, that is a very personal thing in someones life, we don't need blow-by-blow details. Keep in mind that Harry respects women, he could have taken advantage of Romilda's advances, but he didn't. I think he will be a good boy and wait till post-book seven so that the readers arn't watching.