I have just completed an upgrade to Windows 7-X-64 ultimate from build 7137. I used the "change sources==>csversion.ini" method to allow upgrade -- worked fine. I'm using the version available to technet subscribers.
I NEED the laptop tomorrow and I didn't want to re-install all my software and drivers
Finding webcam, card reader driver
etc etc is just a bit too much of a hassle currently.
I know eventually I will do a clean install but for the moment this was just too much to do in the time frame available.
Anyway it all works except ==> 2 pieces of software.
1) VMWARE workstation networking -- just simply re-install vmware workstation again works fine.
2) True Image workstation (NOTE NOT TRUE IMAGE HOME).
This program is "blocked due to incompatability". Solution change the TRUEIMAGE.EXE name to TI.EXE and then it works fine. If you do this don't forget to change or modify any shortcut link you have on your desktop.
Otherwise everything looking good.
Note you can only upgrade from Ultimate to Ultimate etc and then only by editing the file as outlined above. Check posts on "Upgrate RTM from RC" for more info.