Julian... thank YOU for all you have contributed here. Many of your fantastic images and posts have inspired me to try the Merrills!
My only FF at present is the 5DMkII with 17-40 f/4. I have not been motivated to use it, however, as I often find myself places where I just wouldn't have bothered to bring such a bulky rig unless I KNEW I was going to need it - and most times, I don't know that in advance. I almost always carry the GX7 and 12-35 and GR with me, so those are the cameras that usually get "the job".
Interesting to read your comment on the DP1M vs. the 5DMkII and 17-40. I've been keeping my 5DMkII and 17-40 around as my "landscape" camera, but I'm thinking I will finally let them go. Wonderful as they are, I have not been so inclined to have them with me. If, as you indicate, the Merrills wind up offering comparable (or better) results, in spite of the niggling "cons" associated with the cameras and software, they will be riding with me most all the time, along with some selection of m4/3 gear as well.
I find that the GR is a strong performer as well, falling somewhere between GX7 with 12-35 and the DP1M, in terms of image crispness and detail. I can see the DP1M possibly edging out the GR, in my stable, as time moves forward.