We've had one shooter have a Z1 pack it in due to heat but the camera was in a cover in the hot Australian sun.
Any camera will have problems if subjected to fast temperature variations causing condensation. In general cameras should perform better at low temperature, less heat = less noise.

I have used 1080i with the Z1 and have never seen any artifacts. Possibly with 720P you will see them. I use mine in full auto.

JJK

Well, all formats need to managed when you shoot because they all have limitations. That said, the clip below was shot using the Z1 and one ther camera that you would laugh at. The Z1 did all of the racing footage and a lot more, except the interviews. We did not have any problems as described in other posts about artifacting etc. We were carful to select the correct shutter speeds etc for each situation. We were conscience of the best methods for all formats.

The piece below is a student project.
Yes it was edited very quickly in Vegas 6

http://amediaprof.com/os

As Keith mentioned, all compressed formats (and uncompressed too) have some requirement of thought process. The motion artifacts people bring up are usually related to poor choices of shutter or aperture settings. I'll suggest that no one has ever taken an HDV camcorder faster than I have, at 202 mph in a very unstable environment, and the footage is stunning, and has been seen on a variety of HD broadcasts such as HDNet, CNN, and other HD shows.
Just spend time learning the camcorder, testing speeds, and understanding where it works best for your particular application.

The frozen lens cover story was probably an incident mentioned by DSE, where he was filming in snow. A small mechanical fault developed which prevented the lens hood being shut in the normal way and because he wanted to keep out the snow he used a little force to shut it . He then posted instructions on how to disassemble the hood (and fix it) in case this ever happened to anyone else. I believe freezing wasn't the cause.

If it's related to my specific incident, that's exactly true. The lens hood froze up and I damaged it. No mechanical faults with the cam at all.
FWIW, we used several Z1's on the Guiness World Record skydive event where we were required to have a cam rolling at all times. The static cam ended up with condensation in the eyepiece, lens filter, and all controls in spite of using a warmed raincoat. All worked well.
these aren't super-cameras capable of leaping tall buildings in a single bound, but they do take a serious beating.