I think that there are far more levels than are mentioned.
A few of my favorites in no particular order:
When you discover that MAP, inside C3D will NOT query any objects created by C3D.
When you discover that MAP will NO longer offer the user the option to use DBase 5 format when attaching a data source.
When MAP reports attach EXTRANEOUS data to the TXT file one writes in the report mode.
When you discover that in order to lower the start or end invert across a pipe run, that only ONE pipe is adjusted and the remainder of the network remains unadjusted. Requiring the user to edit every pipe invert in the entire run manually.
After five releases the Alignment object and the parcels are STILL not dynamically linked.
The the corridor model STILL produces what Autodesk refers to as "malformed data" in your cross sections unless you manually create the surface boundaries.