Fact of the matter is there is no reason computers need to be made any faster than they are currently. I would say realistically we reached that point somehere around 2008. Productivity would increase so much faster if software was simply coded much more efficiently. What can you really do in OS X Lion that you couldn't do in Mac OS 9? Yet the requirements are infinitely higher. I personally blame it on the proliferation of high level programming languages. A real OS upgrade would be to find a way to maintain the level of functionality whilst decreasing system resource requirements.