I have noticed comments a few times now from Sencha implying that everything can done in the base classes (via designer) and it should be rare that any code is developed in the implementation / override classes.
While in theory this may be the case, I find it does not apply in reality (at least not with us).
In the app we are developing it is actually quite rare that we do not add code of some sort to enhance the functionality of a particular view / store / model / controller.
I would suggest that once an app progress beyond a few basic views inherent complexity will follow and this will require bespoke code.
I would be interested in anyone else's thoughts on this...