After seeing a friends device running the dev preview and reading the overwhelmingly negative feedback from wpcentral see link(wp central link) and their forums the Music app seems to be a massive and unacceptable step backwards. They are hiding the FM, no access to other A/V apps like youtube and last.FM, broken backwards buttons ect.
Also seems to be some rumblings about games spamming your app list since they are no longer centralized in one place. Whoever is making these decisions needs to reevaluate. I agree that the hubs made WP what it was dismantling them especially if it is a step back in terms of performance usability and features is awful. They claim they are doing it to improve the speed they can update these apps separately faster but if takes months or a year just to get back to feature parity its not worth it.