I think it's kind of mute to set the GM1 against the BMPCC other than Andrew did - show that the video side of this little box is also unexpected great. One is a happy little work-pony, the other a high velocity bonsai-cheetah. RAW is better than AVCHD? Yes, it better should. But AVCHD is not all that bad.
GM1 is a 700 € sneak & carry lightly photocamera that has, nearly as a side-effect, great video. Have mine since yesterday and it is really interesting what it is able to achieve. And it comes with a slow but excellent zoom. I may later get an BMPCC too, if my wives budgetary plannings allow it :-) ...and yes, this one is probably in a different class .... but also price-wise. For good reasons.
For people who also want to take excellent photographies & video & want to get a pack of features coming with the camera, the GM1 is an excellent addition, especially to an already in place MFT system. And Andrew is right - my Voigtlaenders started a new love affair with this one.