I think you can be up for the upgrade price even from V6.x OEM.
I have a Nero 7 registration (free upgrade period), but only now am I even thinking that V7 is fit to be allowed out of beta testing..
Remember, Ahead did this to us with 6.0 (released as little better than beta), the repeated it with 6.3 and 6.6 as well ... to the old adage, "never trust a .0", can be added "nor a .x.0".
Pretty well expected that they would release V7 in a similar condition.
The ONLY reason I considered V7, was the TV card support... just hope it does mine, as the software that came with the system has nothing to recommend it!