When your PowerPoint process helps you to clarify your ideas, it turns out you can make an effective presentation whether you use your slides or not.
Garr Reynolds tells a great story about someone who used the Beyond Bullet Points approach to structure a presentation. When the presenter met with his potential client, the conversation naturally transitioned to the main points he wanted to cover, and before he knew it he had won the business and the meeting was over. He left disappointed that he didn't get to use his slides, until his wife reminded him that closing the business was his objective, not showing the slides!
Where does your own center of confidence reside -- in you, or on your slides? When you undergo a critical thinking process that clarifies your ideas in your mind, it shifts the center of confidence from your slides to you. With the center where it belongs, you will be clear no matter what tool, technology or medium you use to expand your ideas outward.