I guess the fact that it has a great cast and a lot of black humour is what makes it so fun. But it has a good script, nice sound and that thick accent is funny as hell.
As some other guy here said, movies that show a lot of interconnected subplots that elevate the level of intimate knowledge about the characters is unlikely to get old, at most it is in danger of being done to death.
Bottom line: this is an Irish "Crash". I found it well done and funny, although a bit slow at times and you have to strain your ears a bit if English is not your mother tongue. However, I advice against translations, as you risk getting something an illiterate 10 year old thought he heard, like I did :(
