So, are there any dead pixels with your Z4, or are you concerned about "just in case"? While I don't have much experience with LCD projectors, I can tell you that with LCD computer monitors, it's pretty hard to notice a dead/stuck pixel. It took me about 6 months to notice that my 19" LCD monitor had a stuck pixel (always white even with a black screen), and that's by looking carefully for them with my face way closer to the monitor than I normally would have it in daily use. After I noticed it, I soon forgot about it, and haven't given it much thought until I saw your post. It simply doesn't affect my daily enjoyment of the monitor. That was 3 years ago.
I've read that LCD screen makers have continued to refine their manufacturing process, such that dead/stuck pixels are increasingly less common. While I realize that LCD projectors don't have the same panels as monitors, my guess is that the underlying technology is similar enough that similar improvements have been made in other LCD devices.
When I've look at the images from LCD projectors in the store, I have to walk fairly close to the screen to see the individual pixels, much closer than I'm likely to sit in real life. So, my guess is that if you sit far away enough from the screen so that the screen door effect isn't noticeable, you're likely to be far away enough that you won't notice individual pixels anyways. Plus, moving images (movies, TV, etc) have enough "noise" in them that would further make individual pixels less noticeable. You may be more likely to notice individual pixels if you use the projector for static images or as a computer display, but again, I doubt it'll affect your day to day use, unless you're one of those people where just knowing there's a defect eats at you ... in that case, there are medicines that help with that ...
