IT Kitchen chimes in with:
The final result is quite the same, human readers don’t know how these formats are different, it’s just not their problems. Developers create different formats, and your readers read the one you chose. By providing old formats and versions you do not contribute to the Web’s progress because people will still use old aggregators.
You know: they’re right. It’s sort of like when the web standards project started and web designers realized that supporting crappy outdated browsers is terrible for the long-term health of the internet. Of course, the hurdle in user-adoption is always a headache – but so is choosing between RSS 2.0, RDF, XML, Atom and Klip.