I loves me the FAQ.

Inflicts critical, causes critical, etc. counts the same as +1 critical and they ALL STACK. And you can trigger the CR of your weapon with a Sigmar's Comet -and- with enough Boons. Loverly.

Certainly ups the lethality, doesn't it? I like how it builds a spiraling decline of your ability to fight, until your wound threshold takes over, you pass out, convert one more W into a crit, and then you die!