I may be a relative newbie to anime (having only been an Otaku for 10 months), But with my friends huge collections I've been exposed to a fair amount.  and this anime made me say "Wow... Sigh."  It's the first and only anime I've seen without huge supernatural powers, Mecha or Marital Arts.  I like these things but in their absence the story becomes all that much clearer. there are many levels to the plot, and it mirrors real life at that age.  WotH is also a great insight into the life of a Japanese family/society.
    An anime that has stolen my heart and mind "If you Listen Closely/Whisper of the Heart," is a great story with the multiple-level interaction that happens in real life and some of the best animation/art I've seen.  Check out some of the more dedicated pages (and this Txt file which I used as reference) below.

Cool Whisper of the Heart Page
Anime Turnpike