The problem with Sails is that unlike Rails or Django, it's not very popular. This not only means a lot less documentation and help for you but also help for the maintainer (financial or code-wise). This means a slow rate of development, bug fixes, and updates.
I do agree with another poster in that if you want a opinionated just works stack, use Ruby or Python.
I am starting a new project soon and I played with Sails. I really liked it, except I struggled with the user authentication part.
Also worried that the momentum of the project seems to have slowed down a bit, Mike does a lot but seems a bit lonely... Or?