Have you tried the Windows Easy Transfer tool? For a test of that a temp install of the 7 RC was seen on an extra drive where the backup made was then restored completely.
That included custom folders as well as the usual user account folders and even things like the wallpapers set with the DisplayFusion program for dual monitors. As the restoration was inprogress the default desktop stretched across from the primary to secondary display suddenly saw the same two separate wallpapers set as they had been.
The compression of some 232gb was down to about 95-98gb total. For going from RC to retail however you wouldn't want to be restoring programs but seeing fresh installs of each for the obvious reasons. But you can pick and choose which files and folders are archived for restoration later once you have the retail installation up and running properly.
For running out of space and seeing more then you bargained for as far as size you have to remember that folders contain sub folders within sub folders where some are not visible by default. You have to calculate the actual size of each once you have taken ownership and made hidden files and folders visible.
You may inadvertently included restore points along with the folders you selected which would also explain why certain files seemed much larger then you assumed.