I have the cad m179 and really like it a lot. It's very clear/transparent. It doesn't seem to pick up as much around the room so that helps if you don't have a good acoustically set room. Good for mic'ng acoustic guitars/drum overheads. Also well liked to be used in stero pairs.
more info here:
I received the M39 (M179) today and had a few minutes to work with it. It didn't sound great with the guitar amp up loud but low volume recordings sounded good. This will require some experimentation I suspect. I tried it for vocal recording and it sounded great! I'll try recording acoustic guitar this weekend and post a quick clip.