Doohan had a chip on his shoulder that he made well known, because he saw himself as this highly multi-talented actor who was unable to realize his potential on the show, because his role was quite small compared to Captain Kirk and Spock. But just look at what happened to him afterward. He really didn't do anything noteworthy, not one production outside of Star Trek that you could easily recall off the top of your head.
Jason of Star Command
The Ben Stiller Show
That's all I got.
As for original point, I respectfully disagree. I don't think Ellison (Not the most trustworthy source i know) made up that Shatner was counting his lines, or that Nichols had to be the one to make Shatner see that he really had been an ass.
Now it's completly possible Shatner wasn't aware of it, and that there is an element of the others enjoying the attention they got by getting together to trash Shatner. But overall, if I HAD to choose between viewpoints...I would say that Shatner had been something of an ass.