SlideMagic slides always looked a bit different because of the Roboto Condensed font. A recognisable style, plus a narrow font that can hold a lot of text on one line. In the latest update for beta testers, I am putting Helvetica/Arial back as the default, making Roboto a second choice.
I see many users using SlideMagic as a starting point for a conversion to PowerPoint, as most of their colleagues have (yet) no idea with SlideMagic is. SlideMagic files with Roboto in them will gave unpredictable results for users who do not know how to install custom fonts on their machine.
Usability is #1. Hence, the switch, but with an option to fall back on Roboto that can get saved as your default font in the settings tab of the app.