No. I changed directly over a 6.06 version(using grace period offer). I’m using win 7 ultimate 32 bits (only 4 Gb of ram). But if you use 64 bits and certain plugins(like waves 9), I think that a demo to test all your plugins will be much safer than move directly to 6.5 full version.
Here some info:
Edit: Now I noticed that you already posted there.
Some folks tried to rename or move Cubase folder, but I don´t know if it was a complete success.