Design Thinking has become increasingly popular across different disciplines. However, what it exactly entails is becoming more and more vague, leading to the term being used for many different approaches and applications. This paper presents an interview study with experts on the application and training of Design Thinking in academia and industry. We find a divide with some seeing Design Thinking as a mere toolbox of methods, while others see it as an umbrella term for the mindset that determines how designers think and act. Subjects unanimously attest the approach large potential to support certain types of businesses, when applied under the leadership of trained designers, but see a lot of danger for the approach to become meaningless if it keeps being advertised as an all-purpose problem-solving tool. The interviewees further share extensive experiences on specific success factors and pitfalls in applying Design Thinking in practice.