Re: What does everyone know about Spock Prime? [probably spoilers]
While having Spock Prime in the movie didn't completely offend me, I think that scene should not have been in there. I liked Leonard Nimoy's exit from Trek in Trek '09, the cameo here was kinda silly.
Plus I thought Nimoy was very strict and gung ho against cameos, that a character should never just be there to be there. Nimoy has always had this thing about characters should always advance the plot or otherwise be dropped. In the TOS movies he directed back in the '80s, he always gave the supporting players key roles to play to move the plot along, they were never just background props. Nimoy refused a cameo in the first TNG movie Generations b/c he felt Spock served no purpose in a flimsy cameo role. I guess he's had a revision on that sentiment.
I don't know - as I said, I think Spock Prime will have a bigger part in the next film - showing his work on New Vulcan and completing his character arc. If so, this was a simple 'Hey, I'm still around' for the character - it established that he was still on New Vulcan and is just a stepping stone to the next film.
Soon oh soon the light, Pass within and soothe this endless night, And wait here for you, Our reason to be here...