I'm fine with the cameo and here's why:
1. Calling Spock prime is research. At this point in the film, Spock is interested in Khan's character. Is he a decent but misguided person, or an untrustworthy SOB?!? Spock prime personally knows Khan so he would be considered a primary source. He probably knows more about the person of Khan than a secondary-source such as the Encyclopedia of Starfleet.
2. It's more fun watching a conversation with Nimoy than having someone stare at the ship's database.
3. (SPOILER) It serves a very distinct purpose of tying this film to Wrath of Khan. Everything that happens between this point and the point where Khan flies his ship into San Francisco parallels WoK with Kirk and Spock doing "what you would have done for me."
The above said, I'd hope (and imagine) that Spock prime will not become a crutch for the Enterprise crew in future films.