MPJ has a wonderful video about meta-work and false productivity and it is well worth your time.
But Plugins (Extension) can improve you performance and usability. Like:
- Vimium for Chrome, or vimperator for Firefox etc…
- snipmate, Emmet for Vim or Emmet for Sublime Text
Sometimes very small plugin improve you usability and productivity, like ToggleWords :) Some help you optimize workflow — WakaTime.