It's true that you can't treat the type as text anymore (if you can select it, it's probably not OK to share the file), but, importantly, you can scale it to any size with perfect fidelity. That's what you don't get in any process involving round-tripping through a JPG.

This is surely an annoying process bound to put anyone off of commercial typography... unless you're already typesetting your presentations in Illustrator. Which, admittedly, I haven't been doing. But now that I think about it: I do a lot of stuff in Illustrator, and Illustrator is so. much. better. than Keynote.