The Model View View-Model pattern gained a lot of momentum lately. It allows to reduce the code in the code behind class of a form or user control to a minimum. Therefore, unit testability is improved dramatically compared to other view patterns like MVC/MVP.
However, when I design software, I follow (amongst others) the principles of SOLID (link).
The first principle in SOLID is the Single Responsibility Prinicple (SRP) that states that “A class should have one, and only one, reason to change.” (link)
And here start my concerns about MVVM.