Superb movie, will not be understood by younger teens and kids
I would rate this among the top three or four movies I have ever seen. It is one of the only movies I have seen multiple times in the theater. It is funny, sad, compelling, insightful, surprising, and completely original. A true classic (at least to me).
As for kids, I think older teens would get it and have fun with it, especially those who are somewhat heady and intellectual. If you are not comfortable letting your kids watch movies with sexuality, avoid this one, as the sex discussion is very frank (though in no way gratuitous).