Does attempting to develop some sort of game, even just as a hobby during leisure time provide useful (professional) experience or is it a childish waste of time?
I have pursued small personal game projects on and off throughout my programming career. I've found the (often) strict performance requirements and escalating design complexity have taught me some of my most useful programming lessons.
In these projects to name just a few, I very quickly came face to face with: "Everything is fast for small N". I also discovered the hard way about using basic object oriented design principles to manage complexity.
In a field where many technologies and topics can be quite dry/dull, I think hobby game development is important in motivating new (and not so new) developers to brush up on essential skills while having fun at the same time.
This question talks about hobby projects in general, however here I am more interested in game projects specially and how valuable they are to professional programmers.