What was unclear in the previous model? Sounds like there is less granularity now on testing the different branches. This could have he effect of bugs being caught later in the development cycle.
The Beta channel is not representative of the Release channel user behavior or hardware either. About 60% of the Beta channel users are in India and Indonesia. The story I heard was that, years ago, someone distributed a CD with a Firefox 4 Beta among their friends in India. It went viral and those people have, unknowingly, been on the Beta channel since then.
Chrome's Dev channel is a nice middle ground: Dev is just a ~weekly known-good snapshot of the Canary (Nightly) channel that has received some QA. Chrome Dev and Canary have the same major version number.