There were some scenes that were really funny, but it was pretty weak overall, mostly because:Warning: Spoiler! (Click to show)
Ricky Gervais' character had almost zero internal conflict over lying to everyone in the entire world, yet somehow was supposed to be likable; the plot was ultra thin, by far one of the least dense movies I've seen in a long time; and the whole "god/religion" thing was stupid, not because I have some problem with the notion of god or religion being challenged, but because it was done so poorly.
Also, the bar scene was such a letdown that it dimmed the whole movie for me. When you get Louis CK, Philip Seymour Hoffman, and Ricky Gervais in a scene alone, it should be magic, and it wasn't even close.