You might want to check out version 13 which was still just an extension of Inkscape. So if you know Inkscape, creating presentations should be easy.
Tutorial: http://sozi.baierouge.fr/pages/tutorial-first.html
Other than the Powerpoint alternatives seen in office suites such as WPS, OpenOffice, or LibreOffice, there is also Sozi which is something that I think you would probably like.
For a Prezi like presenter, as an alternative to impress.js there is also Sozi Inskape plugin. Or for a more traditional presentation look at the jessyink plugin.
Did you find another alternative?
Looks like Sozi is making progress, but still a bit choppy and slow.
I wouldn't mind using Prezi, but they won't let me make own themes and use the company fonts.. (very strict business profile)