First 100 Users is praised for its practical and actionable marketing ideas, particularly appreciated for its free tools section and the concept of building tools as a funnel for a main product. Users find it easy to navigate and a valuable source of inspiration, helping to spark or refresh ideas. While some suggest expanding on the strategies, the overall feedback highlights its effectiveness in providing clear, step-by-step instructions and well-researched examples, making it a useful resource for startup founders and makers.