In the next 2 to 3 weeks I will publish a few blog posts about importing data to PowerPivot using Analysis Services as a data source. This is something I studied a lot during the beta test of PowerPivot and it is not a topic that has a place in the upcoming book about PowerPivot I wrote with Alberto Ferrari. I will make a few considerations about possible improvements in future versions of PowerPivot, but I will also try to illustrate what are the possible workarounds available now.
I will update later this post with an index to the blog posts I will publish on this topic.