The music, for one thing. Seatbelts is an awesome group and I wish I could find some of their non-Cowboy Bebop music because I would definitely listen to it plenty.
The story is probably the best part in my opinion. How mysterious Spike's past is, and yet how clear it becomes without even having a character recount the occurrences. And then the ending itself, that's something else. I won't spoil anything, but if you see all the stuff that happens in the first 24 episodes then you'll know why the last two are so open-ended.
Art, geez, that doesn't even need to be said. Some of the visual effects they use can ordinarily only be captured on film, and yet they use most of them to the nth degree. Their portrayal of certain scenes are so perfect that I don't think Hayao Miyazaki himself couldn't have done a better job.
All in all, 10/10 because it's just that great.
