I think Nimoy talks about that Briefing Room scene in I Am Not Spock
, or else it was some interview I read. It was a pretty big deal to him and he really thought the scene was great. He saw it as serious, thoughtful, sensitive, artistic. And to a lot of fans it certainly was/is.
On the other hand, a non-fan could be forgiven for thinking that Nimoy had felt confined by Spock's usual personality and, when he had a chance to emote freely, he went nuts with it and chewed the scenery.