No, it uses a custom scraper written by Marco. I've found that both of them work better on some pages and worse on others.
(However, I do believe the "Safari Reader" feature of iOS 5 and Safari 5 does use Readability to extract the contents.)
(However, I do believe the "Safari Reader" feature of iOS 5 and Safari 5 does use Readability to extract the contents.)
Also of note, the original Readability was actually "partly inspired by" instapaper (http://lab.arc90.com/2009/03/02/readability/)
Out of the 50 sources I had (regular RSS updates, etc.) InstaPaper failed on far too many, either stripping important content or pictures and captions. Readability was only a bit better
I glued together an app that will pull in RSS, send each URL to diffbot, and then collate the output into a reader that I use. Never thought of releasing it as an app, I just use it myself.
And thanks for suggesting Diffbot, will try later.
From your comment I expected it to be an open source implementation, but a high-quality SaaS with 50,000 API calls/mo on the free plan is still pretty damn good.