I use my browser Canvas to create content, but I rely on the Teacher app to access the content for my courses when I'm in the classroom or otherwise away from my desk. The Canvas features I need most are the files (syllabus and aids), the Attendance taker, and the Calendar (to look at upcoming deadlines or activities).
At this point the only feature that I cannot access via the app is the access to the Calendar.
Wouldn't that be nice?