I bought it on DVD the other day, and I've just finished watching it.
The book was superb. I loved everything about it, a lot. But to say they're slightly different is an understatement.
Half of the events and characters in the book aren't even talked about in the film. Then there's the fact the bloke has an important role in the film. Then there's the fact a load of it is just made up and totally new.
I know its 'based on' the novel, but I'd be pissed off if I was Capote. The feeling you get about the characters is almost the opposite of what you'd gauge from the book.
The worst thing was the ending though! You HAVE to keep the same beginning and ending to the book, don't you? But no, it keeps neither, and ends with them both in eachother's arms. WTF.
As a film on its own, it was ok. I don't think I'd have enjoyed it really, if it wasn't for Audrey Hepburn's appearance. She's probably the most beautiful human to have lived.