Finally, the reason that I have second thoughts about upgrading to Win8 was that I had to search the web to find out how to switch the bloody thing off! This is symptomatic of the whole UI, I feel. There's no way anyone could naturally figure out that you need to to get the Charms up, select settings, then Power and then select Shut Down. Ludicrous usability. With Win7 you see the 'Shut Down' button as soon as you discover the start menu (which is easy to find).
I had the same problem with the developer preview.
And then again with the customer preview. For a tablet Windows 8 is nice and ahead of iOS but for a desktop it's not going to work.