Focus lock can be a challenge but I found it was more about flash durations.
its actually deadly accurate with autofocus and that I really needed lights with short flash durations for moving subjects. I had bowens before but now using pro b3 packs. The camera handles well and I shoot tethered and untethered with it easily. The image quality is great but at first I noticed it wasn't just down to the camera and back and that it really puts a strain on technique. So I had to start being more cautious of how I shoot. I tried the 150mm and realised there was a whole world of hassy goodness I was missing out on. The 150mm is definitely my next purchase.
I still use the d3x for certain shoots but when I get home and open up the files 9/10 times I wish I used the hassy.
The screen isn't great for image reviewing but it's ok. Other than that its a great tool.
Hope this helps.
I was looking in the mediumformat forum (I like your Mofo dog ) and noticed that you has a Hassy H4d-50 and a Nikon D3x. I have a Nikon D3x and are interested in moving in to the mediumformat segment. On thursday I will try out a Hassy H4D-50. Are you satisfied with your Hassy? How is to work with in comparison to the Nikon? When you take a photo of Mofo in motion, is there any problems to lock focus? is there a big different in image quality?