It isn't the teleprompter that is the issue. ALL people who have access to a teleprompter use them in lieu of written notes for major speeches these days. I have used a teleprompter myself, though I vary from my text and add extemporaneous comments so much, I invariably return to the written notes to find my place in the speech.
The issue is whether the person knows and is committed to his/her message that s/he is giving. The teleprompter and/or notes are to keep things moving smoothly, not inadvertently leave something out, not get stuff out of order etc. But most people know their material cold and can talk about it extemporaneously quite easily.
President Obama has proved time and again that he often doesn't know his material and he often sounds like an unprepared and uncertain kid caught off guard with a question from his teacher when he has to wing it without notes or a teleprompter. It is obvious he does none of his own research, and he doesn't write or probably even approve his subject matter as well as not having a firm grasp on concepts he pushes.
Not a huge confidence builder that he knows what he is saying or what he is doing or that he holds firm convictions about any of it.