The service Sheldon Brown provided to cyclists worldwide cannot be overstated. It also becomes apparent every time one needs to research some bike subject involving any technology that appeared after his death.
The overhead exists when a novice is trying to use Vim the way it is intended to be used in order to learn. Using insert mode to get the same behavior as non-vim and avoid normal mode is, in my opinion, bad learning practice.
I think an important part of the Vim workflow that I haven't seen mentioned is the fact that -at least for myself- it keeps the mind engaged during "menial" operations.
When switching from dealing with the information included in the text (typically thinking about code content) to operations of moving text around and other text logistics, I often find my mind "waiting" impatiently for my hands when using non-vim editors. In contrary, when using vim (I consider myself a mid-range user), I can somewhat remain closer to the flow.
At the same time, I still remember (albeit vaguely) a significant overhead of the Vim language before becoming acclimated.