I think it's brilliant. As for "pretty slim girl gets abused" - well, pretty, slim girls exist, they are sexually active in school, and boys and men rape them - so while I always wish there were people less 'attractive looking' on tv, in this instance I didn't watch this thinking "this is unbelievable" - I watched it thinking "she looks like a girl from my school."
If they were ugly teens, it could easily slip into standard apologism "well only ugly boys rape, because they, like, have to." or "Ugly girl gets raped, well she should be grateful, LOL!" - I don't think the fact that they are conventionally attractive/nice looking is a huge distraction from the message.
I like the way they filmed it, as the scenario is one that a lot of people would recognize as the first time they had sex, or a time they were assaulted. Ithink it's got some good choices, for example that she says no and stop verbally and non-verbally, that he hears her say no, and that he basically ignores what she wants/feels. I think it's a powerful message.