I'm a long time Phase One MFDB / C1 user and recently picked up a Sony for personal use. With a small location job, I decided to go with the Sony and use it tethered. Running C1 Pro 8.3 and OS X 10.10.4 I came across 2 issues.
1) Using live view, there is no way to rotate the view, meaning if you shoot in portrait mode, the live view is locked in landscape view. There is a very recent thread on the Phase forums dealing with this, with Phase suggesting the fault lies with Sony's SDK. I think that's pretty lame, to suggest their engineers unable to fix a rotation issue.
2) When tethered, every time I turned camera off / on or disconnected the usb cable, the file naming using "camera counter" did not maintain counter sequence; with each start, the counter number seemed random, including previously used numbers. I've submitted a support case without response yet.