I originally wrote RSS.Style using XSLT, but Google, as the malevolent friend of the open web, is deprecating XSLT (flamewar on Hacker News). So I switched to JavaScript, which (as far as I can tell) works everywhere.
It is pretty easy to add: just a single line to the XML of your RSS/Atom feed: you don’t need to host the script (though you can if you want to: it is MIT licensed).
I feel that RSS and Atom are being held back by the poor (or non-existant) user experience for new users. Try to put yourself in a new user’s place:
Or even worse:
For some reason, technical people just don’t seem to get this. RSS and Atom are not just for technical people. They are for everyone. So the user experience needs to be simple and easy to understand.