Two jobs ago, I built reports and dashboards, mostly in Excel. It was a nightmare. After three years of that, I did some demonstration of Python's capabilities and ended up working on a web-based enterprise reporting system.
These days, I work almost 100% in Python. While I'm not doing analysis much, iPython is awesome for "exploratory programming" - I can quickly build a function to do what I want, thoroughly test it, then import the and its associated tests back into my "real" environment.
The ease of integration external datasources alone makes Python extremely attractive for Excel.
I can easily imagine using iPython to control a small cluster of Amazon instances, using them to process some offensively large dataset (e.g., US Census data), generating a usably small resultset, and dropping it into Excel at the end to make pretty charts that don't look (visually) out of place with the rest of the executive's presentation.
You'd end up with Excel being the GUI of an arbitrarily powerful network of computing resources.