I caught a bad one too - there's a bright pixel almost right in the middle. I used it to read about an hour yesterday since I can't return it till monday anyway, and when I turned it on this morning, there was another bright pixel in the upper left corner as well as a bunch in the lower right corner. However, these are not as prominent as the other two.. they look a bit like, eh, glowing dust I'd say.
I wiped the screen off (not that it was dirty but who knows), but that didn't improve anything. Pretty weird that they showed up overnight. The shadows at the bottom of the screen also seem far more prominent than what I saw on the store model. The box looked unopened, but the back of the kobo itself had a bit of dust on the corners.
If you want to spot the dots easily under normal light, it's pretty useful to load up a black image or pdf. Of course, this will require setting up the device and logging in first.. thanks a lot to whoever thought that was a good idea!