The questions will be sound quality. A lot of people on here are already stating that they don't know why anyone would buy this product when they can get better sounding products for a similar price. I don't know how anyone can know how good these sound yet. I personally assume these will sound quite good as Apple has made a number of nice sounding products over the years. With that being said, at $550 it is competing with audiophile grade headphones so it needs to at least be roughly in that class.
If it is even roughly in the ballpark of other $500 headphones it is going to be a no-brainer for a lot of people due to the integration with the Apple ecosystem and the stylishness of the build.