I'd be hesitant to have it be your only CCW choice, and it is definitely not the best 9mm CCW. If you can conceal anything bigger, it will be better, and I find it really unlikely the CM9 is the biggest gun you can conceal. A Glock 26, for example, is a lot easier to shoot, holds more ammunition, and is a more reliable design.
I like the CM9 a lot and it will probably be one of the next guns I buy. But it will never be my primary CCW, because its so easy to conceal a double stack, or at the very least, a Shield/PPS sized single stack.