It's fascinating to see the questions asked at the start of this thread in 2008 
Thanks for reviving the thread 
Since then not only has my mother tested but I tested then my late  paternal aunt
Followecd by 2 maternal cousins and a nephew so I can make comparisons across 3 generations. 
My aunts DNA has helped other people identify their Scottish ancestor 
Here's an interesting comparison from  a distant match 
  haven't yet found the common ancestor  .
But a similar one in Canada linked to my Scottish gold prospecting relative . If a match only has 1 Scottish ancestor from shared matches I can tell them which of my aunt's grandparents they connect to