I finally saw this film, and I was disappointed. Spacey kept stepping "out" of the movie to talk as if he was Darin making an autobiography. They also kept stopping the action so Spacey could talk to the child version of himself. It got rather annoying.
Spacey being too old to play the role didin't bother me. However, him being paired with a much younger (and teenaged-looking) Kate Bosworth seemed a little creepy at times. The one saving grace was all of the musical numbers. They were fabulous. I found myself tapping and singing along at times (although the power in the theatre went out during my favourite Darin song).