Hi Fez,
Apple, like many manufacturers, is very cagey about exactly how many pixels can be considered enough for a panel replacement. 5 is a lot, especially in the middle of the screen, and I would say that you should contact them. I know a lot of people with MacBook Pros (about 5) and none of them have dead pixels.
The "trick" to getting your screen replaced is to be very nice about it. Most service people will treat nice customers well, while ones who are being rude will be treated by the book, which in this case, publicly, is very vague.
Apple's official policy on dead and stuck pixels is outlined here -
http://docs.info.apple.com/article.html?artnum=22194
Good luck.