I'm really into it and think they did a great job. You get all (or at least most) of the H5D=>H6D improvements (1/2000th flash sync, better screen with touch, dual card slots...no 100MP option though) in a package a fraction of the size and weight and a fraction of the price of an H6D-50c. I'm finding it hard to see what's not to like about that. It looks like they kept the button layout and interface simple as well, a gripe I have with existing mirrorless cameras. The wheel by the shutter that pops out I think is particularly clever (no accidental settings changes and keeps design cleaner) and it looks like the grip is well thought out as well. I had been hoping to move from my H4D-40 to a used H5D-50c or H6D-50c, but the X1D is a much more attractive option for me and most likely would hold me over for a couple years until prices on the H6D-100c come down.
Also, the size/weight is a game changer for me in terms of portability. Being able to tote around MF like I do my A7R and carry it around all day when I travel is HUGE. It will also draw a lot less attention because it's much less conspicuous, something I grow tired of with my H4D. Traditional MF size may be advantageous in the studio to impress clients, but outside of the studio the attention is annoying and the size/weight makes handholding all day impossible. Of course I can still use my 35-90mm on a tripod when I want to, something I prob won't be able to do if another manufacturer puts out a mirrorless MF. I'm really curious to see if in addition to an H adapter, they make an HTS adapter for H =>X1D.
The only downside appears to be with no FPS the use of 3rd party glass via adapters may be a no-go, but this is not a big deal for me as I've sold off most of my glass that I would adapt to mirrorless. I'm also concerned about heat buildup and noise with long exposures, as well as battery life. I do love the OVF of my H4D, so I'm curious to see how the EVF compares and if there's focus magnification or any of that that I've grown used to with the A7R. The X1D may not be perfect for everyone, but it checks all the boxes for me. I'll try to demo one and if I like maybe order around the holidays if I can. I also want to see what happens at Photokina before ordering...there's been rumors of lots of other cameras (mirrorless MF Fuji/Sony, 70+MP Sony 35mm FF, etc) that may change the landscape considerably. Even if it's not the camera for you, there's been talk of mirrorless MF for a long time, and it's nice to see it become a reality.