This is a very simple movie that tests the iPod Touch and iPhone screens. It plays black, white, red, green, blue and a nice scale at the end. Check if you have any dead pixels and it your blacks are the correct way around, not displaying the 'negative black' issue that so many are reporting.
In our early findings, having seen six iPod Touch screens, none that we saw had any display issues. So this cannot be something that is effecting every Touch, it must just be certain ones.
The video can be downloaded here. Then drag it into iTunes or onto your device and touch play.