This movie definitely deserves to be watched - and to be rated (by those having watched it!)!
It is absolutely funny, sometimes makes you laugh out loud, sometimes simply makes you shake your head delightedly. It is different from any other movie I have seen so far and has been one of my favourite movies of the last 5 years at least. If you need comparisons: The one with the Coen Brothers is probably one of the best. One particular movie that came to my mind while watching "TH" was "Very bad things" - maybe that helps...
Terribly happy has a great story, told in a rather slow tempo, the main characters are very well developed - but whenever you think you know them, there'll be something happening, that makes the whole thing turn into another direction. Very psychological, strange, sometimes irritating, on the other hand beautifully photographed, always surprising, simply lovable and most of all damn funny - that's what "Terribly happy" is!!!
(sorry for my english - this was my first movie review ever...)