I’m not entirely sure it’s seamless. The color timing of the live action shots is much less saturated in the unaltered versions. Also, they only use the original mono audio.
I really have not noticed that, the only shots that were unrestored were the special effects shots and that was because they were too far gone to save.
As for the audio you can just switch to the new surround sound mix using the audio button on your remote and watch the original versions with the new audio mix that way.
I have to say that while there are places where I would have like to see a better restoration job done(More in line with what was done to old Doctor Who DvDs)so far I have been pretty happy with the Bluray releases of both TOS and TNG and I wish someone had been able to show this to Lucas and explain to him that this was all we want. I would still pay for the SEs if the GOUT was included the same way it is with the TOS Blurays.
I can’t speak for anyone else but that is all I ever wanted.