Been doing some research latley around the ModX content management system (CMS) and concrete5. What I've found is that while the approach of each CMS is similar I found that the implemenation is different and that is where the devil is in the details.
ModX is seems to us to be very hands on and as such isn't for the less technical user. If you are willing to work your way through it we find it is a robust system. There is always a learning curve that comes with any CMS, but that curve seemed to be more challenging than it should be. Adding a form to the website and then getting to work the way I wanted to was a bit frustrating and the documentation that we worked through didn't seem very clear.