What percentage?
the replacement i got has the same issue, i know atleast 3 people with the same issues...loads of people talking about experiencing the same exact problem
http://discussions.apple.com/thread.jspa?threadID=1947029&tstart=0
or google for it, just about every mac forum has topics of people having the problem.
barefeats website talked about it only 5 -6 days after the release back in juli...up till now not a word from Apple and was reading a few days ago on a forum that some other poor kid just had received his mac pro and was experiencing the same problem meaning they are still shipping out computers with faulty hardware...way to go Apple, you are truly a quality brand!