I have to admit that I have not tried to use Google Presentations, though I do use Google Docs & Spreadsheets. The reason simply has been that normally, if I am creating a presentation, it is for use at a speaking engagement of some sort, and that means I want to ensure that it runs on the projection system and PC that will be on the dais, and that it can be copied and viewed by attendees later, in a format I think they will use. Microsoft PowerPoint, in other words.But Google coders have enhanced the Presentation application in ways that immediately made sense to me. Presentations now can be saved in a file format that allows them to be embedded directly into Web sites. Now that is something one cannot really do with a Microsoft Powerpoint.
In fact, there is now a new use case. If I want to create content in that format for Web distribution only, I don't have "native application" issues. I can simply embed the presentation directly onto a blog or other site. Cool.