Given the amount of coverage I've given Hartikainen over the last year, there isn't much new information to put out there. I recommend you browse the copious Hartikainen wing of The Copper & Blue library; there is information on everything from his propensity to shoot from in tight to his play in the World Junior Championships.
Where does that leave Teemu as he heads to Oklahoma City to begin his first North American season with the Barons? Well, we're not really sure. When I last looked at comparable players, it became clear that the Finnish military service requirement makes it difficult to use any kind of one-to-one projection for teenage Finns. Right now, his closest comp falls somewhere between Ville Niemenen and Jere Lehtinen, and the gulf between those two players is wide. If he does turn into Ville Niemenen at the NHL level, I don't think you'll find an Oiler fan, nor writer here, that would be disappointed.
His season in Oklahoma City will tell us so much about his game and his future. He's moving to a much smaller rink which should allow him to use his physical game and be a more effective winger. At the same time, he's going to compete against larger men, on average, and that should limit his physical game, especially power moves from the boards, something he lives on in the offensive end. But he's more than that - he kills penalties, he was KalPa's version of Tomas Holmstrom on the power play, and he both enjoys and excels in the defensive end, or at least he did in Finland.
There remains every chance that Hartikainen will flame out and never sniff the NHL. Gabe Desjardins looked at the issue last year and gave him a one in three chance of making the NHL based on historical rates. But the kid has a jet stream worth of wind behind his back right now and he plays a game that no other prospect in the organization plays. He's come from nearly nowhere and has been forced to prove himself at every turn; there's a crack in the door and if anyone is capable of wedging his way into the show, it's Teemu Hartikainen.