Canvas is a new LMS that just went open source last week created by Instructure, Inc, a company “founded in 2008 with the purpose of disrupting the Learning Management System (LMS) market by setting a new, open standard for education technology.” See
http://www.instructure.com/about-us

Instructure posted  a series of screencasts last week on YouTube, see:
http://www.youtube.com/user/CanvasLMS).

The Chronicle quotes Josh Coates, Instructure’s chief executive, describing Moodle as “kind of kludgy” and Sakai as “off in left field a little bit” (see: Upstart Course-Management Provider Goes Open Source).  Dr. Chuck, the chief architect of Sakai, posted an open letter to Instructure on his blog, urging the company to infiltrate campuses virally.  Michael Feldstein was astonished by the completeness of its features.  Inside Higher Ed gave is 7 cheers and 7 critiques.  eLearners.com praises it ease of use and excellent design.

Seems to me that Canvas focuses on what it most important in an LMS, assignments and grading and has a well designed workflow for these activities.