I know a few developers that use VIM as their IDE. These are people that has worked as Linux/Unix sysadmins for a decade or two before becoming full time programmers. They were competent VIM users afters spending countless hours tweaking server configuration or writing shell scripts. It came natural to them to tweak VIM even further when they started programming in higher level languages.

For new developers however, I would not recommend using VIM as an IDE. That is simply torturing yourself when there are so many good graphical IDEs with code insights, debuggers, built-in doc, code completion templates and so on.

As you mention, having a basic VIM knowledge is important though, since you will find it installed on pretty much all servers, and you can’t rely on more easy to use tools like nano. If you take the time to learn 10–15 VIM commands, it should be enough to get you going with the ad hoc file edits in VIM.