When people start up Watson, the software polls his site to see if there is a new version. As part of that process he collects what version of the OS they are using (I wonder what else it collects?) and here is the results so far:
46.4% running Panther (10.3)
52.4% running Jaguar (10.2)
and 1.2% running Puma (10.1)
Thats a quick adoption rate if I do say so myself, even though you have to take these numbers with a grain of salt since its only based on Watson users, but still not to shabby.