CM and Altium are quite far apart but you can jump from one to another without much of a learning curve.
If you are new to ECAD, it is a great bit of software.
The recent 2.0 update has made it even closer to Altium but without all the bells and whistles.
A lot of people will suggest KiCAD over it but it really depends on what your needs are.
CM is so much more user-friendly than KiCAD full stop.