Almost every site I look on has at least one, and probably more, people who are going to write their own operating system. What's the point? When its finished the chances are nobody is going to use it - probably not even you.
I might not mind spending a few hours on a whim, but, mercenary sort that I am, if I was going to spend a couple of years on a project I would want to be able to sell the end product for hard cash.