I watched it. I generally enjoyed the movie. I found the dialogue, especially, to be very realistically awkward in necessary scenes. You should have mentioned Julia Stiles was in it! What I did have trouble with was the idea that Julia Stiles would find an unshaven David Cross "cute," but that's okay. The ending felt rather as if the writer didn't know how else to end the play/movie/script. I also think this movie tries to say more about relationships, or wants to say more about relationships, than it ends up saying. I think it does a very good job at showing human beings as what they are, which is mostly silly beings who care very deeply about things that seem inconsequential to everyone else. I thought it was very realistic in that sort of way. I found Hedy and the conspiracy-theorist-dude's relationship least convincing. Dude seemed to me to be more of a "younger brother" maybe "annoying younger brother" figure than "equal friend/party to the action." I had this sneaking feeling the whole movie long that the event was going to turn out to be false even though the movie never encourages this idea at all. I think it's just a trap of suspicion that you run into when you have elaborate or crazy situations happen in seemingly everyday settings.
I actually re-watched it yesterday because it was raining and it felt like the thing to do. It wasn't as good as I remember, but I agree that the dialogue was one of the stronger points. Julia Stiles with David Cross was a bit of a stretch, but I think it was partly to outline the fact that she's been with a lot of crazy guys in the past and was trying to settle for a more normal boyfriend. Maybe she reasoned that a "less cute" man at this point in her life would be more likely to be both single and mentally stable. I've got to say that I enjoyed the ending. [vague spoilers ahead] It kept to what I thought of as the theme of making yourself comfortable in unforeseen and awkward circumstances. That's not the best way to put that, but I think it's clear that none of the characters are where they thought they would be in their relationships, and that the ending was a kind of collective and grudging acceptance of everything going on. Plus, I can't think of any better ways to end it without taking away from the realistic universe that it's set in. And Shane's paranoia/conspiracy theory attitude definitely made him my least favorite character. They could have fleshed him out a bit more rather than just using him to be an annoying foil (for pretty much everybody's laid back attitude) to shit on.