I think they do a disservice by talking about what this "could be". I don't think the emailing and mapping stuff they showcase is really as useful as the whole concept/package. It's really almost like an internet command shell with a lot of clever extensibility.
Out of the box reaction: I love it.
My first session was: I just hit ctrl-space and up comes a black command prompt. I type in letters and as I do (because they don't match a command), it does a Google search as-I-type. The feeling of narrowing down my results as I type from Google is really great. (If Google just did this on their own site, I'd be quite pleased. It makes me want to write a BOSS search engine that does this. The responsiveness just feels great. I know MS tried this at some point with Live, but it just didn't feel this good.)
But then there's a zillion other things I can do. I can leave twitter updates just by typing "twitter #myconference This keynote is boring". I can digg the page I'm on just by typing "digg".
Some of this will feel a lot like keyworded bookmarklets in Firefox, but it's really the next logical step from there.
Imagine if you could leave a comment on a page supporting Disqus just by typing "comment This site is great! Good idea." without scrolling down, clicking into fields, and typing. Imagine if I could do Socialbrowse commenting/sharing without navigating dropdown menus.
Then there's the fact that these little commands are really easy to write and add to your site. As soon as you visit a site that supports them, Ubiquity tells you "There are commands that work for this site. Click here to subscribe." and then from then on you can execute those commands. So if you want people to search your site easily or maybe accept friend invites, or invite a friend by email, etc. They can do that from within this console easier than clicking around.
Maybe it won't catch on with individuals, but every power user or developer should be playing with this and thinking about what they could do with it.
</passion-burst>