Free service and free apps? Whats the business model?
I was interested in supporting them, but because I already support Marco @ Instapaper with a monthly donation, the Readability subscription (was it $5 or $7 per month) wasn't worth it for myself.
You couldn't have an account at all without paying before. Now, you can sign up for an account for free. With that includes a 30-article Reading List, (optionally) public profile, and access to the apps (device syncing, &c).
Premium users also get Archives, an Unlimited Reading List (mine has 1000+ articles in it), daily Kindle digests, and —of course— the warn fuzzy feeling of supporting the writers that create the content you enjoy.
The list is likely to grow in the future.