All you have to do is answer the question: What does Sony have that Apple needs?
The answer is: Nothing.
Music, movies, one of the biggest gaming brands in the world, Devices which could be rebranded to apple.
Put that all together and I think apple can use a lot of that.
Also financial services is a nice division that makes a lot of money, wouldn't hurt to have that.
EDIT: Also don't forget all the patents apple would be getting. SOny is in the top 5 patent holders in the US