Can't just be renamed 'iso' files surely..
indeed. 2.1GB for the x64 seems a bit small....
Maybe they're for updating from the Dev Preview?
No
They'll release a full ISO
If im not mistaken the dev preview has built in image mounting. Perhaps ESD is a windows 8 specific image file. And thus must be installed from windows 8 developer preview...
sourceWindows 8 Consumer Preview Build 8250 (8250.0.WINMAIN_WIN8BETA.120217-15) is available for download now. The Windows 8 CP 32-bit and 64-bit Electronic Software Distribution (ESD) versions has been leaked much before the official .ISO release. Though genuine if you are not a developer or a consumer with prior knowledge about ESD it is adviced not to download it right now as the official ISO release is imminent.
Thanks! 1.7MB/sec for me.