Yes, it is true that the iPad doesn’t do PowerPoint.
(Ironically, since I started the draft of this post, Microsoft has actually released an iOS app that allows—perhaps limited—PowerPoint editing as well as presentation.)
It’s also true that it does do Keynote. There’s a good chance you’ve seen a presentation that was powered by Keynote instead of PowerPoint. I’ve used Keynote on my iPad to edit and present a presentation that was originally created with PowerPoint. (There were some issues but nothing that kept me from getting what I needed done done.)
More interesting, though is that the iPad does Haiku Deck. Haiku Deck doesn’t have all the features of Keynote or PowerPoint, but what it does, it does well.
And that’s only two of the presentation apps for the iPad.
Oh, and Keynote works on the iPhone and iPod touch as well as the iPad.