With JSON Feed, it’s not about disrupting RSS exactly. RSS is great and widely deployed; it’s not going anywhere. But we can take what was good about RSS, improve a few things, and maybe jumpstart new tools and apps that work together. Developers use JSON everywhere now instead of XML, and Brent and I felt that maybe XML was even holding RSS and blogging back.
As I thought. These are great reasons for JSON Feed to exist.
The rest of the interview is worth reading as well.