Well, I thought it was great!
I thought this film was great, but there seems to be more criticism than praise for it on here, so I thought I'd try to refute the main criticisms and at the same time try to say why I thought it worked. Just want to say now that these are my opinions only and I don't intend to ruffle any feathers by this, and it's not aimed at any specific people, just the general feeling from comments and reviews I've seen on this site.
The most frequent complaint I've seen about this film is that people say it is "not funny". In my opinion it is funny, but it is subtle and of a smaller scale, much like real life day-to-day humour is. I think people's tastes are spoiled by the fact that so much humour we are exposed to here (i.e. a lot of American stuff) is all cheesy slapstick that's just not at all sophisticated and very in-your-face. So when people create a film with more realistic humour, everyone complains that they're not wetting themselves and falling on the floor rolling around in hysterics, or as one reviewer on this site said, that there were no "large-scale comical incidents". Now, I don't know about your lives, but I laugh a lot, as do my friends, and I can't say I experience "large-scale comical incidents" very often... and I'm not sure why in an entirely improvised script, anyone would expect anything so artificial. I thought it was a hilarious film because it was realistic, because although the whole "competition" was a ludicrous idea, that the humour generated by the characters was great, because you can identify with bits of it, be it the overly-negative interfering mother-in-law, or the competetive, confident girl who everyone knows is painfully insecure. Yes, I wasn't dying of laughter, but this film made me laugh a hell of a lot more than most "comedy" does, simply because of how real it was and how excellently the actors performed their roles.
Then there are people that complain it was "boring", again I suspect this is because most people expect (hugely unnatural) laugh-a-minute japery when they see something advertised as a comedy, which is a shame. Granted, Jimmy Carr's presence in the film was exaggerated by the trailer, but given that I'm not much of a fan myself, this didn't disappoint me.
I've also seen people criticise this film because of its allegedly "bland" characters. Again, are people really spoiled by things like Friends and all of that American cheesy humour that their characters have to be big, bold and completely artificial? Yes, because I'm sure in real life your friends can easily be pigeonholed as "the kooky one", "the neat freak", "the nerd" and so on (!). The characters in Confetti, whilst obviously stereotyped to a certain extent, were believable as actual three-dimensional people, not just devices used to engender ridiculous "comic" situations.
At the end of the day, if you don't find it funny, you don't find it funny. Simple as that. I just think it's a shame that what I think is a gem of a film has received such negative reviews simply because it doesn't fit the hugely Americanised idea of what a "comedy" is meant to be, and because people expected differently. I went to see this film with an open mind and was both humoured and touched by it, something that doesn't happen to me very often at the cinema these days. So to conclude, I'd recommend seeing this film if you haven't already, and try to appreciate it for what it is, instead of expecting it to fit neatly into the comedy genre.