I am also I windows 8, and have been for about 2 months (plus about two weeks of CP). I overall think its a good OS, but there are quite a few downsides. I think you will find alot of these over the next days and weeks.
As for the blog, I would suggest a paragraph a day + any other things you think of. I think you might want to make a blogspot or tumblr(?) page for it though, as it would be more steam line with less interruptions compared to the forum. Then you can just link.
For content I would suggest you give your opinions on the UI (a big deal among some people) as well as talk about which (if any) apps you use. I personally use the Mail, Calendar, (sometimes) and people apps, and suggest you at least give them a try.
After that, after a few weeks or so, you might want to talk about bugs and issues, as there are quite a few (I find it to be quite unfinished) all the while you can just give general user experience points.
I think that this is a great idea, and look forward to reading what you have to say. Don't forget to pick up a free copy of windows media centre (unless you dont want it), if you haven't already.