Thanks to a dead battery in my battery box, I had my first experience going mic-in with my M10 this week. Mics were CA-14 cards, show was a solo guitarist but pretty loud. I dialed the gain back to about 3.5 to allow for some headroom, ended up peaking around -12.
The result sounds great to me, surprisingly so given the poor results I've gotten going mic-in on past devices. Those of you with more M10 expertise, are there certain situations where I'm going to see a huge bump in performance by going CA-14>battery box>M10? Or should I feel safe dispensing with the battery box when I want to travel light?