This is my impression after 30 minutes of fumbling with it:
The look for end-users is clean and feels great. Way better than Blackboard for end-users. Canvas seems to promote a more self-service adhoc approach which would be attractive for small installs.
Unfortunately the admin interface seems non-existant.
How do I sanely create and populate thousands of courses?
User admin tools are primitive. Where is the ability for the administrator to change a users password? How can I see what classes they are enrolled in, what their roles are, etc? Can the administrator globally disable a user for non-payment without deleting?
How do faculty roll the content from one course into multiple sections and then roll that content over to a new course next semester? No anti-cheat integration?
Anyway those are the concerns I was able to find in the first 30 minutes.
It looks undeployable here which is a shame. Here is to hoping it gets better soon.
Edit: I just spotted the course copy functionality. Scratch that one off the list. Still not impressed with the central admin tools exposed in the UI. Our faculty would prefer not having to populate the user lists in their courses, etc.
Edit 2: Thought I'd be done playing with it but not yet. I can't get over how awesome the end-user UI is. As I just sent off to a co-worker: "The end-user UI is stupendously good compared to Blackboard. Stunningly good in comparison. It's like taking the best of Facebook and turning it into an LMS. Hide this from users."
Definitely has my interest.