I spend most of my time developing complex BI solutions and, doing that, I always talk with DBA, developers, CEO, data analysts and the many kind of people that work around a BI solution. Nevertheless, in these last months, publishing posts about PowerPivot and teaching the PowerPivot course around Europe, I am keeping in touch with the vast number of people who really use Excel to solve their daily analysis problems and, with no surprise, I am learning that I am very ignorant about Excel capabilities.
This last post of mine has received many interesting comments from Excel users and the previous one got some useful comments too. Many other posts are scheduled in the next weeks, so I think I will get more interesting feedbacks. Now, I don’t have any problem admitting that I am not an Excel guru and, probably, I will never become one. That said, it is clear that a good knowledge of PowerPivot (something I am supposed to own) is not enough to create a true PowerPivot solution. A very good knowledge of Excel is necessary too, to create all the complex functions needed to automate steps in the building of intermediate tables, reports and all the fancy features of a good Excel solution.
Thus, the question I am wondering about today is: will BI professionals need to learn all the insights of Excel (i.e. BI to Excel) or are Excel guru going to learn all the complexities of building a BI solution (i.e. Excel to BI)? The truth is probably somewhere in the middle. Nevertheless, I tend to prefer the second scenario, where Excel power users will learn PowerPivot and some fundamentals of BI development against the other one. The rationale behind this opinion of mine (apart from my laziness in learning Excel) is that it will be easier for Excel gurus to learn BI development than for BI professionals to learn how to leverage all of the Excel functionalities.
Excel power users already have a strong knowledge of their real world scenario of data and will not need to read the many books about data modeling to start playing with PowerPivot. Instead, working by trials and errors, they will create simple data models that will help them to create some first reports and, one step after the other, they will learn how to build a complete BI solution, at least for their specific needs. On the other hand, whenever I try to write some VBA code to automate a process in Excel, I am lost in the vastness of its features and functions and soon spend more time trying to write the code, while my time is better spent in data modeling. Thus, I believe that the Self-Service BI road will be full of Excel people learning the basics of BI, with very few BI professionals learning Excel. But… my opinion might have been guided by the fact that I find BI easier, since I already know the topic. 
Nevertheless, if you are serious about introducing PowerPivot technology in your company, keep in mind that you will need to have both strong Excel and PowerPivot skills. Excel can no longer be considered simply a “BI client”. In the PowerPivot era, Excel is becoming more and more an active part of the BI solution with all of its programmability and functionalities.