I found it to be a very good emulation of vanilla Vim, but also found when I was using Vim mode I hardly used any of the IDE features aside from passive JSDoc/outline/etc displays. That lack of integration between the two halves killed it for me, not to mention it'd been a long while since vanilla Vim was what I was really using.
I love the Language Server concept and hope that just becomes the thing going forward. There was never any reason specific language knowledge should be part of the editor, other than we didn't have a vertical enough ecosystem yet to coordinate a different way. Whatever else I can say about Microsoft, they accomplished that vertical pretty skillfully with VSC and TypeScript, and have been running with it like mad. I'm glad some of that has been to our general benefit.
I think you can change that to only on file save, though.