I still maintain that using OmniPlan as I suggested is no more difficult or time-consuming (you're hardly using any of the features) and can easily do what Graham described of his paper system — it sounds like what I did in my example.
I have used MSProject and integration with Outlook, and I have used the JCVGantt Pro addin with MindManager that also integrated with Outlook. Once I started using these tools for project management, I immediately saw their potential for personal time management, but...
In both cases it required too much effort and time, up front, and to maintain, when all I need is a rough idea of whether June is going to be a busy month or slack month. The return on the time invested just wasn't worth it for me.
As I said, the Month perspective that I have now created almost does what I want and it only involves hitting a hot key.