Yahoo just released a whitepaper on RSS usage [pdf] and a publishers guide to rss.
A summary of their RSS findings are:
• Awareness of RSS is quite low among Internet users. 12% of users are aware of
RSS, and 4% have knowingly used RSS.
• 27% of Internet users consume RSS syndicated content on personalized start
pages (e.g., My Yahoo!, My MSN) without knowing that RSS is the enabling
technology.
• 28% of Internet users are aware of podcasting, but only 2% currently subscribe
to podcasts.
• Even tech-savvy “Aware RSS Users” prefer to access RSS feeds via user-friendly,
browser-based experiences (e.g., My Yahoo!, Firefox, My MSN).
• My Yahoo! has the highest awareness and use of any RSS-enabled product.