Most of my software development career was spent working at a small company that sold a product that emulated the operating system developed and sold by a much, much larger company. The work was interesting and when you had a breakthrough or a small victory, it sure felt good. The challenge of keeping up was exhilarating and kept folks motivated to keep pressing forward.

But eventually it wears you down. It's nearly impossible to keep up in the long-term. Normal product evolution, the sheer size of the behemoth and sometimes even malice on their part to thwart the little guy make it really tough to stay current.

Think of Wine vis-a-vis Windows. They will never catch up.