Is this really practical for the average front end developer. Appart from the dev tool upgrades (which are awesome, I'll admit) I only forsee spending extra time fixing features that may exist in canary, but aren't supported by other browsers. Rendering differences between different versions of chrome and general browser degradation problems.
I've worked with devs who used Canary as their default browser. Two bugs during my time with them were bounced back with "Cannot reproduce." This was because they were using Canary.
In another instance, though, a dev tested in Canary and fixed a bug on a site before it hit the users.
This is my experience – sometimes I fix/work around bugs before users get them, sometimes you have to accept a site is broken in Canary, but you know it won't be in the stable builds.