It's just not the same as with Eclipse. I'm not sure what it's called or if it has a name, but the Eclipse equivalent to VS Pro's IntelliSense, in which it's actually aware of code that you've previously written in other files or third party libraries, and it pops up as a little list next to what you're typing--is it possible to have that level of functionality in Vim?

It's the actual awareness of code you've previously written, the detection of possible issues before you compile--IDEs tend to read your code with you and help out a lot in many more ways... I suppose it's not "autocompletion" but I was hoping to successfully use that as an umbrella term.