I've also used it on our PgCert L&T in HE and at a recent session of student group presentations 3/5 groups used Prezi in lieu of PowerPoint or Keynote.
It's clearly striking a chord with some colleagues and I wonder why. There's some interesting research to be done here I think. My hunch is that it's partly discipline-specific with those in visual-rich areas (e.g. healthcare, art and design) most to gain from the ability to zoom into uploaded images.
I read an interesting comment on a Kingston University Elgg blog post from a colleague who was drawn to its non-linear potential that fitted well with the theme of her lecture:
I used Prezi (in place of PowerPoint) in a seminar last semester. It was relevant to the content of the lecture since we were discussing the digital future of 'books'. One of the key differences between physical and digital books (aside from the feel and smell!) is that physical books are linear. You tend to read one page after another, one chapter after another. Of course you can dip in and out and use the contents or index pages to find the material you want. But most people read an old-fashioned book more or less sequentially. Digital books, however, provide opportunities for presenting information or stories in a non-linear fashion. Prezi, therefore, was the perfect tool to not just talk about, but demonstrate, the non-linear nature of new technologies.
Kimberly Scheideman, in her blog post A Beautiful Sunrise - PowerPoint or Prezi - What's the Difference? makes a similar point. She claims that Prezi suited her thematic presentation of Eoin Colfer's novel Artemis Fowl better than PowerPoint ('I felt the Prezi captured a concept that a PowerPoint couldn't'). So, in other cases, it looks like the lecture topic or structure is informing lecturer preferences.
More thoughts on this later but for now here's the handout we distribute in our sessions - comments and corrections welcome.