Well I decided just to try it out and it all installed quite smoothly. I havn't checked all the functionality yet but there didn't seem to be anything untoward.
I used the Win7 USB Boot Tool to create a bootable USB from the ISO but for some reason I couldn't get it to boot (up arrow + power on switch on should do this?) So I just hit setup from within the developer preview and opted for a clean install.
I am not averse to doing a complete fresh 'proper' install should it be required but as I say, so far so good.
(I am currently installing Visual Studio 11 Express onto the Build Tablet)
I will let you know how I get on.