First reaction after watching this movie: "Holy F*cking Shitballs, what the Hell is wrong with these people?". The movie's main message, apparently, is that a smelly, awkward, dorky and ugly guy with a gigantic nose can get Hayden Panettiere to fall for him by proclaiming his love for her despite never having talked to her and then being awkward and saying obvious and clichéd "deep" things for an hour and a half. So I did what I always do in these times of confusion: Wikipedia. Upon reading the description of the book this is based on, I think I know what went wrong here: casting.
Now, don't get me wrong, Panettiere was well-cast and totally believable in her acting... the problem is the dude they cast as Dennis. There is just no way anyone could ever fall for someone like this, and the way he acts in the movie makes it impossible to believe in what is happening. However, if the guy had been at least somewhat approachable, then the movie could have worked, because the writing itself was pretty decent and could theoretically happen. Just not with this guy.
With that said, this is still a pretty funny movie, if you can stand the suspension of disbelief that is required, and it certainly shows some originality. Plus, in the original book (and, I imagine, the script), the attempt at making nice guys more appealing is certainly commendable. So it's worth watching, if only for burning that mental image into your head. And Panettiere, I guess.
In a sentence:
Commendable for its attempt at making nice guys more attractive, but fails miserably at it thanks to the casting/portrayal of an unloveable and pathetic nerd. Still, pretty funny, and Hayden Panettiere.