All valid arguments, really, but we all know that VHD is a virtual HARD DISK, and some really clever coding skills are required to convert it to ISO, so that it can be used to install Windows.
Personally, I'd find it far easier to just mount the VHD into Virtual PC and use it from there.
Or, as I believe was the original intention of leaking a VHD file instead of ISO, is to allow Windows 7 users to virtually mount and boot directly from the VHD. I do not recall where, But I remember reading that Windows 7 had the ability to use VHD files as boot devices...
Me? I'll stick with 7100 until GA on 22 October 2009...