Fair question ;-). It goes back into the history actually. Back in the day when gold miners used to carry canaries with them as a way of "measuring" poisonous gas leaks which is still one of the main risks concerning mining in general. Anyhow, for some reason if there's a poisonous gas leak, then the poor bird would die before anything happen to the humans... so the miners used the bird as a way of evaluating danger, in a way.
|A "real" Canary!...|
That's exactly what you get with the Google Chrome Canary version. Google or the Chrome developers use the Canary edition as a way evaluating the stability of the browser before officially releasing it. This is the first time it has been released for Mac OSX users!, and anyone who wants to download the "Canary" version should be aware of the fact that, it's actually could be unstable than the official daily developer builds as well.
|Yellowish logo ....|
But if you're interested in "testing" or getting the cutting-edge technologies in web browsing... and a fan of Chrome, then Mac geeks :P, this is your moment!.
Again remember, these builds aren't even tested manually before releasing, although not all the time but there could be bugs or especially major security related bugs!. So before downloading it, please take those things to account.
Anyhow, unless you're going to use the Chrome Canary in Mac OSX to store your passwords or log-in information, only going to "browse the web" then those concerns may be slightly lower. Also, once installed the Chrome Canary will get automatic updates as well. So if the developers discover new bugs and fix them... then the browser will fetch them automatically.
So before giving it a try... make sure you understand the risks and good luck.