The biggest plus you get when using CScope is the ability to do a "reference" search. You can find all references to a given symbol in your project quickly and easily which I find invaluable for refactoring (what's going to be affected when I change this?).
One thing to realize is that vim IS an IDE of sorts. Only, it's far more extensible for the same effort. (although, from my brief forays with emacs, emacs certainly beats vim for extensibility)
Cscope, as commented on the article's website, sounds quite interesting too.
ctags -R --c++-kinds=+p --fields=+iaS --extra=+q .
export CTAGS='-R --c++-kinds=+p --fields=+iaS --extra=+q'
And what about tokens created using the token pasting operator ## from include files that are included multiple times (e.g. code generation hackery)? Visual Studio will at least locate the include file which introduced the token, and of course will be able to complete on the token, aware of its type etc.
Ctags is great, especially for navigating someone else's code. What does this function do? Just ctrl-] and suddenly I'm at its definition. Something in there I don't recognize, same thing. Ctrl-t to go back up the tag stack. Ive become so used to navigating my code this way I have trouble without it.
Completion is just the way that Vim will give you completion matches in insert mode if you hit ctrl-n or ctrl-p. With C it's very smart about it and will automatically search included files. It's great for not having to worry about exact spellings on things. If you really like this sort of stuff there are a few plugins that do Textmate-like snippets.