advice on stuck pixels:
1) don't look for them
2) if you want to look for them, ask yourself the question: do i really want to know?
3) ask again
4) if you still insist, go to versiontracker.com and there are many utilities to turn the screen into basic colors so you can check
apart from getting hold of a very generous store employee, there's no way to make sure that your PB has no stuck/dead pixels. if you buy it new, open the box and the number of stuck pixels do not go beyond what's considered "normal" by apple, you cannot return it without paying the 20% re-stocking fee.
also, since federal regulations prohibit any new box opened being re-sold as "new," most stores will not let you open up the box to look. unless you want to buy the store-demo machines that has no stuck pixels, you really don't have a way to take a look before you buy. you can only look once you buy because the second it's opened, i can only be re-sold as a refurb.
we can debate all we want whether this situation is fair or not. it's the fact of life at this moment.
lastly, just don't look for them. they are usually hardly noticeable, especially if you don't know where they are.