The concept is pretty cool, and the execution is fairly decent as well, but this film feels very flawed and somewhat unpolished. Some social and philosophical questions are asked through the story, but it never gets brought to the next level, and there's no real conclusion to the whole "first guy to discover lying" part of the story. On the other hand, the acting was surprisingly good, the humour was very Gervais-esque and the fantastic cast list didn't hurt either. Also, ignoring the huge amount of contradictions in the main plot, this definitely is a movie that makes you think about it afterwards. For that alone, it ranks higher than any other RomCom in my book.
In a sentence:
Feels like it's bumbling around and fiddling with a few different concepts without really knowing where it's going. On the other hand, the actors and acting are great, and the story forces you to think.