Being Roddenberry, Berman, Braga, Jeri Taylor and such all have differing definitions on what is and isn't canon, it's hard to take the concept very seriously.
It comes down to opinion and I can form my own. I'm sure you can too.
The difference is they worked on the show and you/we don't. Their's is more than an opinion.
Not really. They're men, not gods dictating what we should and shouldn't think.
Roddenberry really did pick and chose what he thought was cannon.
Berman said anything on screen is cannon, which contradicts Roddenberry's comments about TAS not being canon and hinting at ST V and VI not being so.
Braga said the same thing, then followed up that he didn't care much about continuity.
Jeri Taylor implied her novels are canon and used them as references in some episodes.
A discussion on deleted scenes and such? I think the average viewer is intelligent enough to formulate their own opinion on the subject.
Being the creators can't get on the same page, throwing around "canon" like it's some sort of Trek Bible is contradictory to say the least. Guess it has something in common with the real one anyways.
I enjoy the extra scenes, and think they enhance the movies. I enjoy the books, I think they paint a more complete picture of the Trek universe than the movies. So to me they're "real" and if someone in a Paramount office or a random user on a message board doesn't agree, that's their privledge.