Back in August my Nike+ Sports Watch GPS stopped synching. I wrote about the issues here. It turned out that a combination of my update to Mac OS X Lion and the Nike Connect software prevented synching. Online posts told me this affected early watches. I bought mine the very first day it was available.
I contacted Nike and even though my watch was long out of warranty and without acknowledging the issue they sent me a new watch. Works like a charm. Only differences in hardware I can see is that the buttons are firmer and less likely to be mistakingly tripped by errant fingers.