Success in the app industry is no different than success in any other business. It often comes down to how users feel when using your product. A professional designer can be the difference in securing funding or investors for a startup, or pushing your product over the tipping point to mainstream acceptance.
Working current trends into your product's presentation can give your product the contemporary and modern vibe you're looking for.
Great-looking design is useless without taking into account a business’ needs for their mobile offering. Goals vary for each company, and so too should the design approach needed for success.
Is your app primarily functioning as a social tool? An online shopping experience? Perhaps you are after content creation or user signups. This is where my skill set as both an experienced branding designer as well as a user analytics professional combine to deliver an app that is sure to look and feel wonderful in user hands, while serving your business purposes.