View-models

Recently we had some discussions on pros and cons of introducing view-models. I still have some concerns and I'd love to have your feedback.

I do see the benefit of moving code out of the view controllers (a.k.a. "dumb view controllers"): unit/automated testing. I just don’t see why it should go to an extra layer (view-model) instead of going to an existing layer (model). To me “model” is more than just a “dumb” data storage: there is code (“business logic”?) which links the data we store to the UI where we show/the user manipulates it. This code should go somewhere. So far it was mostly the view controller which makes unit testing difficult (but not automated testing - that’s another story). Too bad. I just don’t see why it’d be better to add one more layer (more classes, more files). Simple is beautiful.