Presentation design can take a long time. But most of that time is not spent on the physical activity of putting slides together. The time consuming bit is to come up with the design itself.
Now we have hard data. A SlideMagic beta tester deleted the wrong presentation and had to re-create it from a PDF export. Time spent to create the presentation: 6 hours. Time spent to recreate it from the PDF example: 30 minutes. (Of course, SlideMagic's grid structure made it easy...).
Think about how you can spend those 6 hours most productively. I would take 30 minutes to start thinking about your presentation way before the deadline. Then drop it. Spend time sketching ideas on paper, and then putting the whole thing on slides. And maybe you could have shortened that 6 hours a bit?
I think business presentations should have more standardised slides (a list, a transition, a contrast, an overlap, a growth path). You might say that that will will cause all presentations to look the same. But remember, that standardisation is already happening today: most PowerPoint users only know how to make bullet point slides, even if they wanted to be more creative.
That is what SlideMagic is trying to do: offer easy customisable slide building blocks that are more creative than bullet points but less complicated than hard-to-modify PowerPoint templates.