I can see where you're coming from (healthy sceptism about hyped youngsters) but what makes him special is not only his age but the fact that he has not only easily adjusted every time the bar has been raised for him (i.e. higher Level), but he has also looked as the best player on the pitch almost every single time. Like I wrote earlier, he started the season as a promising youngster (debuted for the senior team in a friendly at the age of 13). Six months into the season and he had impressed so much that he now was a full member of the senior squad. He was called up to the U-21 squad where he impressed against the impressive Portuguese team. A month later he was called up the NT for a friendly. A few weeks later he had played in two more matches for the NT, one of them being a EC qualifier. He impressed everyone in Norway during those matches. During that period he had also established himself as perhaps the best player in the Norwegian league.
So basically he impressed from the get go at senior level in the domestic league, then U-21 NT and last but not least as a full international. All this at the age of 15. Granted, the opposition isn't all that (apart from Portugal U-21) but it still speaks volumes about his talent and ability to adapt. I think what impresses me most about him apart from his technique is his overall matureness and vision. He somehow almost always manage to release the ball at the right time and although the videos circulating might tell a different story, he doesn't 'overdo' his dribbling like a certain C.Ronaldo did in his early United days.
He might be 'ordinary' compared to talents from other countries, this is just my view on what he's done so far that makes him special.