That's a good point. I might phrase it thusly: in order to build up expertise within a solution space (such as doing cool mobile device applications) you end u

That's a good point. I might phrase it thusly: in order to build up expertise within a solution space (such as doing cool mobile device applications) you end up having to stick with a particular platform/tool-set long enough so that your knowledge of the platform isn't a barrier to solving complex problems. It sounds to me like you more or less ended up doing the correct thing.