I am a long time Vim user but I have never ever managed to get c++ tag completion work consistently there. At some point I just stopped trying - went to Qt creator and turned on Vim plugin there. The experience (for C++) is just vastly superior. The IDE integrates with CMake natively, the debugger is graphical and works, the symbol navigation over all project is blazing fast, I have real refactoring etc...

I still use Vim a lot, for JavaScript, for text, for remote sessions... But when a tool with real semantic highlighting and understanding of code is available (with a Vim plugin) then I'll take that.