They used them for my dd. I think they give some extra information, but they have to be taken with a grain of salt. I think, for example that it is useful to better discern areas of relative weakness/strength. The extended norms were an "after thought" so they really don't have the same validation that the regular norms do.

I think they are a good thing and it is important to note the scores with and without the use of extended norms to gain more clarity.