Despite being still a beta:
To keep the familiar and praised usability for consumers of Apple products and the innovative spirit, please take the following into consideration:

• change the overall colour palette of iOS 7 from cute and too colourful to more serious but yet pleasing and classy
• change the overall visual inconsistency and confusion throughout iOS 7 to a more consistent and sophisticated feeling
• make iOS 7 feel less inspired of the competitor's products but more unique and distinguishable from other smartphones' interfaces and nearer to the company's previous efforts
• make text on iOS 7 more legible, by using better typography