You've posted a great example of why 12MP is plenty for the kind of shooting you do.
For me, I shoot mostly landscapes and some wildlife. I print on a 44" printer which means it's not unusual for me to print 40"x60" or bigger in the case of panoramas. For this, I'm often stitching images to simulate higher resolution from my 16MP D7000 & 12MP D300s, and yes simulating 60MP by stitching does show a dramatic increase in detail in a huge print, compared to 12MP. There have been a number of times over the years that I priced a medium format system and decided I just couldn't justify the cost. Given that my D7000 already has similar pixel density to the D800, I see the move as an increase in size, not resolution, or a pre-stitched sensor if you will. It's a system competitive with medium format for under $5000 which is a remarkable thing for someone like me.
Let me say I'm not a "fanboy" and I've always preached (1) photography is about pictures, not equipment (I'll expand on that to say it's all about prints), and (2) if you can't clearly articulate what problem a new piece of equipment is going to solve, then it's a waste of money. So, I'm not so much arguing with you as presenting a counterpoint.
There will be some fanboys purchasing this who need the latest thing and couldn't take a decent picture unless they found someone's tripod holes. There will be some people who buy it just because they have the disposable income. But, like Ned says, this doesn't mean the camera exceeds everybody's purposes. There are definitely people who have been waiting for this camera because it solves some specific problems, and for us the D800 is a revolution.