Thank you for the high praise. We definitely view the API as our main differentiator vs other editors. Hope you will not be disappointed!
Stypi was acquired by Salesforce in 2012 but we continued to work on Quill because we felt it was a missing piece of the web. We're now working for GoInstant (also acquired by Salesforce in 2012), who are also working on some very cool stuff.
Quill was originally called Scribe but then another editor released a bit ago with the same name so we changed it to Quill.