https://blueprints.launchpad.net/dhis2/+spec/flexible-multidimensional-aggregation
Section 2) is updated in the blueprint description.
Basically the status is:
The more fixed multidimensional report tables for canned reporting (e.g. in BIRT) are now working fine. You can now design reports in BIRT combining raw data, subtotals and totals for data elements.
A few more resource tables are needed to be able pull all the data elements dimensions into pivot tables or other OLAP tools. A few examples of what kind of tables that are needed are listed in the blueprint. While this covers what I see as immediate needs there might be other tables needed and other priorities, so feel free to comment, preferably in this email tread since blueprint updates are not sent to the whole list.
Ola