I still owe folks a full write up of my first couple months with the EX1....I won't forget.
Couple thoughts on the Z1 vs EX1: I think Z1 is a great camera. I also think the Z1 was tuned such that UW shooters could get some really good content with relative ease. Out of the box, with a little knowledge of WB, focus and exposure, capturing same great footage was limited only by the creativity of the shooter.
That said, probably the greatest issue with the Z1 is the HDV codec. After shooting with HDV for a couple of years, I am disappointed by how poorly it holds up in post production. I have come to understand why broadcasters have been so "snooty" about it. In good light and slower moving subjects, the codec held up decently. In lower light and faster subjects, the codec breaks down quickly. Underwater, the degree of banding and artifacting can quickly become unacceptable IMO. Add CC in post or gamma adjustments and it degrades further. As much as I have tried to manage variables to eliminate these issues, you hit a point where you can't succeed. One major issue is how the codec deals with blues in lower light. The blue gradient is hard for any image capturing device to nail. With gain locked at zero, I have many shots in open blue where the subject looks tack sharp but the background is banding and artifacting. Come time to sell the footage and I would spend hours trying to 'fix' the unfixable. Bottom line is the bit rate and chroma sampling are insufficient to handle these challenges.
Any of us who have shot with this cam for awhile can point to loads of clips that look great and don't have issues. Problem is, when you have to get the shot and conditions are not ideal, you can be left in the lurch. When it then goes to Post, the production runs into issues and quality must be compromised. Don't get me wrong, this isn't a bash session. I have REALLY enjoyed shooting with this camera and have loads of exciting footage from it. I am just being honest about one of it's major limitations.
I was very very skeptical about the XDCam EX 35mbs codec before trying it. It smelt like a slight upgrade on a flawed codec. It took a lot of work to change this view. Having now shot with the EX1, I can say with great confidence that the Codec is truly a major step up. How and why I still can't say for certain. It seems that HDV was Sony's first pass on compressed HD and they did a good job. It also seems that they took very seriously the complaints about HDV when retooling the codec. I imagine the XDcam Ex codec is greatly optimized and with the additional 10mbs and true 1920 sensors, it has what it takes to deliver. The codec, though not perfect by any stretch, is pretty darn solid.
For me, artifacting and banding are for the most part behind me. The camera can deliver smooth gradients in the blue, even with some gain added in low light. There is very little blotching and artifacting in low light and low vis shots. That said, I am finding the EX1 out of the box more challenging than the Z1. To get great content requires a greater understanding of the camera, its controls, and how they function. I find myself needing to do more shot preparation. I also find that with the larger sensors, the DOF is more limited and the min FD not as good. Much more can be said about this later.
Overall, I don't think it's about EX1 vs Z1. Each of these cameras has its place. When you consider the price point for these cams (plus accessories and housings) respectively, you are looking at twice the investment for the EX1 vs Z1. When economics are considered, it really doesn't make much sense to run them head to head. If your work requires your content to be primary format approved (BBC aside) and your productions require a more resilient and higher grade codec, it makes sense to consider the EX1. If you have much larger budgets, throw in a RED and F900 for good measure

If you don't have these requirements, the Z1 is a terrific solution that can deliver exceptional footage for many projects.
...more to come later.