Hello, and welcome to the user page of a TOS Expert!!
I'm a long-time fan of "Star Trek: The Original Series," and I am somewhat puritanical about it. I don't consider anything besides TOS to be canon Star Trek, from "The Motion Picture" onwards. Every single Trek-related production other than TOS has failed miserably to capture the spirit of The Original Series, as well as failing to maintain consistancy within the universe itself. These inexcusible and easily-avoided flaws make reconciling these differences within the universe impossible - thus the only option is to stand by the original source material as the ONLY canon, until a viable, valid, and properly-executed continuation is produced.
Until that time, "Star Trek: The Original Series" is the only canon form of Star Trek in this fan's humble opinion.
Because I am such a devoted fan to The Original Series, I am extremely well-versed in many aspects of the TOS universe. My status as a Purist has allowed me to conduct research unbiased by influences from the other series which might compromise my accuracy; if I find something that doesn't "mesh" with things from the other shows, I don't disregard it and allow it to be overridden by the information from the other shows - I disregard the other shows themselves and stand by what I have discovered about the world of The Original Series. Because of this I have learned many things about TOS that have long been forgotten or purposefully ignored.
If you need to know ANYTHING about TOS - feel free to contact me by email!! :)