That said, implementing all the basic movement commands and maybe some tag navigation goes a long way towards making any source code editor more useful.

But I concur in that I would also demand macros, text objects and registers to really make it delightful.

Frankly, though, most plugins I use could just as well be implemented as IDE features. Refactoring stuff, project management, debugging... I would not mind doing that the IDE way instead of the Vim way.

ViEmu (MSVC) comes pretty close to that. Vico is on a good way, too.