Rui CarmoBoingBoing has caught on to the fact that there is a lot of bandwidth waste in RSS, but Cory fails to point out that it can also be fixed server-side (unless, of course, your ISP uses dumb transparent proxies).
I've been graphing my site traffic on a per-content basis (apologies in advance for the color scheme), and ever since I started generating RSS diffs, RSS bandwidth has gone down to under 10% (it used to be 30% or more):
(orange for RSS, green for Coral hits, magenta for inline images, blue for site layout components and Flash headers, grey for photos, white for plain HTML)
Nevertheless, the fact that RSS is way larger than plain HTML is still a matter of concern. I will try to churn out comparative plots of both and see what comes out.