MapControl has been somewhat of a bone of contention in my organization too. From what I have been told by ESRI at 9.3.1 the licensing agreement changed in regards to mapcontrol but it is only enforced from 10.0 onwards. Basically you need an Engine SDK license to do any sort of development with ESRI controls including the mapcontrol. That, even if the mapcontrol is deployed inside ArcMap as in a dockable window. This in my opinion is something that was taken away since ESRI had a map control as part of desktop going all the way to 8.1 or 8.0 (I can't remember which.) So the use of map controls far predates Engine and Engine licenses existence. So if you really need a mapcontrol in your development, you need an Engine SDK license on top of your ArcView license (we need it on top of our 23 ArcInfos, Spatial Analysts, ArcGIS Server, etc. and that not only for developers but also for automated nightly build servers and other virtual machines that compile and run automated tests.