The death scene, yeah I knew it was in there, a beat for beat recreation, and before seeing the film I was very upset/concerned about that. It had such an emotional impact on me in 1982 and I thought I would have a hard time with it but as it unfolded, I was touched. Certainly no where near as devastated when Spock died, or even more so Kirk's eulogy after, but I was moved. The film had earned that from me after watching the Kirk and Spock banter in front of Pike, or when Kirk tells Spock he will miss him and Spock starts to say something and then closes his mouth and Kirk is exasperated, all of these character moments they built up for me so that scene and impact.
I think the scene was well acted ("KHAAAAAAAAAAAAAN" not withstanding - but that's a tough one to deliver seriously for any actor, I'd wager

) and well directed.
But the entire time, it left me without any feeling of legitimacy. It didn't feel real because I knew they weren't going to permanently kill off Kirk in the second film. Heck, I knew it was unlikely they were even going to have him remain dead until the sequel.
It was like all of the Next Gen episodes that I despise where the very first scene shows the Enterprise blowing up, so you know it's going to be yet another time travel episode.
It's an obvious gimmick and it feels like the writers were taking the easy out. In this case I knew, even as the scene played out, that they'd have some wacky method for bringing Kirk back.
And I think the death was too soon. What could the stakes possibly be for the next film now that they've killed Kirk? And given that they ended the film with Khan frozen again, they definitely leave the door open to bring him back, suggesting this movie was meant to be more Space Seed than WoK (if you think about the conflict, his beef was really never with Kirk in the film, just like in SS he didn't start out actively hating Kirk, just wanting his ship). So they've pretty much already had Khan do the worst he could do -- kill Kirk. What sort of revenge will he exact next time?
"I've done far worse than kill yo--er, um, I've killed you, and I'm going to keep on killing you, again and again and again."
The Wrath of Khan, on the other hand, had a LOT more depth in Spock's death. From a story standpoint, there was a lot of legitimate set up for Khan's blind rage and his single-minded determination to hurt Kirk. But beyond just the story, the characters had been around for awhile and getting "a" film, much less two, out of a series that was cancelled after two and a half seasons was pretty remarkable. No one really expected a full franchise of films out of it. Also, WoK was filmed amidst Nimoy's very VOCAL declaration that this would be his last Trek film. In fact, he only agreed to be in it if Spock was killed.
So not only did people not know if there was going to be another film after WoK, but they also knew Nimoy was out.
The point is, until the filmmakers tipped their hand and added the planet epilogue and Nimoy's voice over, Spock's death felt VERY real and very legitimate.