It's very fashionable to say nasty things about Microsoft PowerPoint, but there are aspects of it that I really like.
Powerpoint is a structured editor. True a page (slide) is one of the structural elements, which is a pretty major constraint, necessary in a presentation program, but it also has a very clear distinction the difference between presentation, via templates, and content.
Within the content, each slide has a title, and a hierarchy of bullet points and notes (unless, of course you ignore that and put all the content in pictures, which is done all too often).
There's an outline view, where you can edit the presentation and other views that allow you to manipulate a document in different ways.
So, in some ways it's a fine example of the kinds of principles we go on about in the XML world. I have never tried Apple's Keynote, I suppose I should since I am using a Mac now, but OpenOffice.org has a similar thing, which is not quite as usable but has the advantage of built in PDF and Flash export.
I did a little googling on this idea and turned up this from Norm Walsh, part of a long thread that to the XML Dev mailing list.
A structured editing tool is great for XML, but most of the structured editors I've seen think they're doing you some sort of favor by hiding the markup. To me, that's like hiding the punctuation. Sure, lines of text and spaces unbroken by all those pesky periods and commas would be simpler by some metric of simplicity, but they wouldn't be easier (for me) to understand.
Most users coming to structured editing for the first time find all the markup, if not frightening, then at least distracting. So recommending that they use a structured editing tool that hides complexity makes sense. I don't really see it as a goose/gander issue as long as the tool you're recommending has the power to grow with them.
Which seems fair enough, and PowerPoint certainly fits, it's a structured editing tool that hides complexity. Except for the part about growing. Bloating, maybe.
But then Norm has never touched PowerPoint, which is just as well 'cos I think you'd want a two-buton mouse at least to use it, rather than just a long pole.
To keep this on topic, I'll point out that I've never touched PowerPoint or Impress or any of those other tools with a ten foot pole, but I still, in retrospect, create bad slideware. Lots of bullets. I'll have to think about that.