I remember almost exactly the opposite about AJAX (when the paper came out, not when the XmlHttpRequest object was introduced) --- people went ape about what they could use it for. AJAX style genuinely made new things possible. This (supposedly) just makes them cleaner.

Are you questioning the relative merit of reverse http, or of the ability of the server to update the page?

I'm failing to see the advantage of reverse http over long polls, even though I am completely sold on the difference that having server push would make...

The relative merit.

You have a point. But I have to say that I didn't need any imagination to think of ways to use Ajax to enhance parts of my web app interfaces.

The only reason I hadn't use xmlhttprequests extensively before it became popular (and renamed Ajax) was because it was too much work, too error prone. The popularization of Ajax lead to solid frameworks and libraries, which fixed that.