I permanently installed the NC-2 in my Martin OM-28V, and have no regrets. The pickup sounds great and is very resistant to feedback, even with the mic wide open.
Very natural sounding, but you do get a sense of that mag sound, especially with the mic turned off or low. But that is SO much better than the piezo quack in my book, so no complaints.
I wouldn't trust this as a temporary install, with the cable hanging off of the soundhole. The belt clip is useless in my opinion.
Other than that no knocks on this pickup other than price, it is on the expensive side.