I've heard many tales of William Shanter and what a git he is. So much so that I really don't want to meet him if I ever got the chance. He's an absolutely awful convention guest by most accounts, to the point where people call any bad convention experiences with a guest a "Shanter experience" on one convention forum I lurk on.
Having met Shatner, well I use meeting in it's loosest sense, I can confirm that he is indeed a rude and arrogant arsehole.
I can quite understand why the original Trek cast despised him, and those who are still alive, still loathe him. Only Nimoy will talk to him.