I would suggest reading some books on the topic of Dimensional Modeling [1] such as "The Data Warehouse Toolkit" [2]. The critical thing you need to expose to your users is the ability to ask for things which make sense in their world that are actually really difficult for even an engineer to code. Things like: "Show me average 9am-12pm sales on Mondays, Wednesday and Fridays for 1st quarter, 2012"

  [1] http://en.wikipedia.org/wiki/Dimensional_modeling   [2] http://www.amazon.com/Data-Warehouse-Toolkit-Complete-Dimensional/dp/0471200247

I am currently doing reports/datawarehouses/dashboards. When something more complicated that simple questions is needed (see Data Warehousing for Cavemen), ad-hoc queries are quite often not the answer anymore, either with NoSQL or with SQL.

I don't want my clients to be dependent on me (or someone else) to build complicated SQL queries when they have questions, so I focus on getting an easy to maintain facts/dimensions model (as advocated by Ralph Kimball http://www.amazon.com/Data-Warehouse-Toolkit-Complete-Dimens...) which can evolve if needed.

The nice point about MongoDB when doing this is that it makes it a lot easier to add attributes to dimensions, or load the data, or evolve the reporting system in general (and I like that).

You can apply the same principles to build dimensions/facts based data structure and answer questions that SQL alone wouldn't be able to answer easily.

Example of such question: how many calls did we receive during french legal week #9 that were handled by team X outside the normal working hours or while we were in vacations ? In those calls, how many were issued by a woman (as it has a financial impact in this case) ?