Well, I was referring to OS X, not that it doesn't have a command line, but it's definitely not known for it's command line.
OS X has pieces of FreeBSD in the kernel. It actually satisfies the SUS standard which is what an OS needs to implement in order to be called UNIX (though, to actually put the UNIX name on the product Apple needs to pay a license that I doubt they'll ever do). So technically, OS X is in the UNIX family of operating systems. I know a lot of programmers and sys admins who work in OS X and use the terminal daily. The terminal isn't common amongst regular OS X users, but that's just like how Command Prompt (or Power Shell) isn't common amongst Windows users. Also, whether or not it's known for the command line, VIM integrates into the OS X terminal a lot better than it does in Command Prompt or Cygwin. But this isn't very important; I just wanted to point that out.
Personally, I don't see the learning of a whole different philosophy of editing worth the time. Considering how little time is actually spent editing in programming I don't personally see what the point is.
If I have to use a text-mode editor, I'd rather just use Nano. Slower yes, but I don't use it enough for it to matter.
Are you a programmer? If you're a programmer then you spend a lot of time at least viewing source code. So you need a quick and efficient way to browse, search, and link individual and multiple source files; but that's just viewing the source. While editing is only part of what a programmer does, the programmer does spend a good amount of time editing source files; though, the amount depends on what kind of programming you are doing. It's very unlikely that a programmer couldn't benefit from learning VIM -- even if they need to use a lot of third party software. The only real way a programmer couldn't benefit from using VIM is if they really don't spend much time even looking at source.
The only people who would see the benefit in learning VIM are those that actually spend a good amount of time in text files. But even sys admins can benefit in learning VIM even if it's just for config files and shell scripts. VIM completely removes ALL repetitive tasks in editing text files, especially when it comes to just moving the cursor or viewing a specific section of the file.
So for you personally there might not be much benefit in learning VIM -- I don't know your situation. But for someone who edits text files for a living, it makes a world of difference. Even though, as a programmer, I need to do many tasks outside of programming, I still spend a lot of time inside text files. Once I had masted even the basic usage of VIM, it absolutely baffled me how slow everyone else edits text in any other editor.
But VIM isn't for everyone. It takes time to learn it's many features and to be comfortable with them enough for them to become intuitive. I initially learned VIM because I thought it was fun, but I would still use other text editors and IDE's. It wasn't until I spent more time playing around with it that I realized just how powerful it was, how much easier it made my life, and how much frustration it removed because in any other text editor, the cursor keys and the mouse just slows you down.
Today when I program, I don't think about editing the text or how to get the cursor to where I want it to be. VIM give me the power to view and edit text so quickly that I can spend my time thinking about what I want to do instead of how to make my editor do it. Step one is learning how to use VIM. Step two is learning the VIM philosophy. Once a programmer accomplished those two steps, he'll experience an incredible increase in productivity.