This is coming from someone that used IntelliJ before moving to Sublime Text 3 before moving to vim for Python development.

I am by no means a master of vim's varied features but the best productivity gain for me is vim running in the terminal. I use a lot of command line tools (grep still beats most things for search and the git command line tool is still better than any editor plugins), it's just much more convenient for me when it's all in the terminal and I can switch between them seamlessly with keyboard commands especially when using something like tmux.