Given the extremely mashup-friendly nature of PowerPivot, I found this article fascinating:
http://searchsoa.techtarget.com/news/article/0,289142,sid26_gci1372670,00.html#
Especially liked this part (my emphasis):
"Mashups won’t succeed in a BI context unless it’s fun, unless its highly interactive and the user says ‘wow that’s totally easy to use let me use that so I can build my reports,’" said Kobielus. "If it’s approached where IT is forcing self-service on reluctant users, I think it will fail. It’s got to be user enthusiasm that drives this."
"The key is to break up the work a bit," said Robert Eve, EVP of marketing at data virtualization vendor Composite Software. "We work on the data plumbing side. You have your data-oriented people – your data architects. Then you have people more focused on the business consumer and the application usage to work on the visualization side."
It sounds like someone has been reading the PowerPivot playbook 
Actually, I prefer to think that these are very insightful people independently reaching the same conclusions we did – it has to be light, easy, and fun. And no matter how good the tools are, the users still need good, clean, accurate business data, so the role of IT becomes more clearly-defined. Division of labor and specialization always makes for greater efficiency.
Hi Rob, I agree with you fully, i really hope the final PowerPivot release will be very user friendly and very easy to work with for the excel analysts. I have good hopes with the sets and time functions included in CTP3.