Hi,
New to Grav I used it on few project with very basic needs, and it was very easy. Then I needed to implement advance needs and started to have difficulties.
For example I think it's overkill to be obliged to create a custom plugin for the sole purpose of adding a path in the templates locations collection.
And now I have the worse difficulties to implement a not-so-complex form, because of the order of events and data availability. I spent literally few days on it, even tried some smelly hacky ways, but could not find any correct way to achieve what I need. I may be rewriting it using only basic PHP features to manage the form (if grav let me do so).
On top of that the documentation is very basic, and I found some advance things by scavenging old issue threads on github. This is not serious.
Now I'm afraid of what is going to happen when I will need to implement other features. I moved from Rails to Grav on few project because I wanted to try some lightweight framework, but really start to feel Grav is intended for basic needs.
Don't get me wrong, I believe Grav is great, super fast, very easy to learn and use, but I also believe its applications are narrow and it become extremely hard to use with specific needs.