We have some great news to share: we’ve removed the limits on free Readability accounts. All users—free and paying—now get unlimited access to their Reading List, Favorites, Archives, and all our other features.
One detail that had set Readability apart from Instapaper and ReadItLater was that Readability offered a premium subscription service. Users could pay to remove the limitations imposed on the free service. Those funds were used to pay the developers as well as the publishers, bloggers, and authors who signed up with the service.
In fact, that whole subscription deal set Readability apart from just about everyone. None of the app-based aggregators (Flipboard, Zite) charged a fee, nor did any of the reading services (aside from Instapaper and the apps they sold). That always struck me as a little weird; I didn't see how anyone else was going to make a living at it.
But now the free service will be as functional as the paid and that means that there is little to differentiate Readability in terms of cost. Now they'll need to continue to work on offering the best features.
To be honest, I've never used Readability much. For what I needed, Instapaper and dotEpub worked just fine. Both already were free. One supported a bookmarked list of content that I could send to my ereader, and the other let me clean up an article so I could read it locally.