Like some of you, I’ve tried just about every RSS reader out there. I’m more or less using Google Reader and Rojo now, which leads to one of the first serious problems I see with RSS: getting accurate metrics.
There are tools out there to help but many of them don’t have the ability to account for things like multiple subscriptions (e.g., if one person uses multiple RSS readers) and cannot provide detailed demographic information. That means it is harder to monetize RSS content because site owners might not have a correct picture of their readership.
So, even if someone has 5K subscribers, that doesn’t necessarily mean they have 5K readers. My experience shows that somewhere between 10-20% of the total subscriber base is actually consuming content. I’m basing that off of different clients I’ve worked with (as well as my own stats), so that’s not scientific (if anyone has legit numbers, chime in).
Of course, I’m positive RSS metrics will mature beyond what we presently see. In the meantime, however, it’s important to advocate this technology within the context of this limitation.