One advantage of the MEAN stack is that you only need to know javascript to start developing on it, which saves time and brainpower to get started. That being said, I'm curious if there are other advantages to learn the MEAN stack?
The main advantage for using the stack has been a huge time saving in getting the project set up. NodeJS and express is hugely flexible about how you structure your source, which can also be a downfall in the additional mental load of deciding where stuff should go. MEAN does this for you.
The disadvantage has been where I want to do things differently from how MEAN is set up. For example, MEAN uses Bootstrap v2, I wanted Bootstrap v3. It was a slight faff updating it. It would probably be harder if you eg. wanted to use MySQL instead of MongoDB.
There is still a lot that you need to learn before you will get an app fully up and running, but with MEAN you can get cracking on stuff before you know it all. I don't know anything about Grunt yet, but can still use the Grunt file provided to run the server.
Well worth using in my opinion.