I've been reading and watching videos about PowerPivot for Excel 2010 and Sharpoint 2010.  Looks pretty amazing! 

If you've looked at PowerPivot, can you give us some thoughts about PowerPivot?  How does it compare to other client tools you've seen?  What will be the impact for BI? 

From what I can tell, a user doesn't need to build a cube, although you can connect to a cube if you want to, plus you can incorporate data manually from outside the cube into your worksheet as in this example:

business-intelligence.kdejonge.net/using-powerpivot-to-combine-cube-ssas-data-with-manual-data-the-movie

If that's the case, what is the advantage of having a cube in the first place?

Lots of questions, I know, but I'm sort of new to BI, and I'm curious how someone who has been doing BI for some time sees where this product fits in.

P.S. - I thought the MDX designer shown in the video looked very helpful.

I've been looking at PowerPivot since last summer and feel that its place is in the hands of Power Users.

That said there are some short comings that will be manifest them self as hurdles that the developers need to overcome. One of those is many-to-many (M2M) relationships. As I see it you will not be able to solve this in a way that will be simple for the power users. As Microsoft says you really don't need to know that much about data models... but when dealing with 2 separate star models and you want to use them in the same PowerPivot, how can you do that without needing to know a lot about data models. I''ve found one workaround which does help at all. See:

Anybody else got any tips?