I'm pretty certain that Hawaii will match Titan or come really close depending on the game - some games favor nvidia, others AMD. Hell the 780 slightly OC'ed is pretty much equal to the Titan anyway, so either performance target is fine. If Hawaii matches the 780, it's right up there with the Titan anyway. You're only paying for the VRAM on the Titan, basically, no reason for anyone to get it over a 780 since they're pretty much the same speed when you bump the clocks up on the 780 a slight bit. And the nice thing about the 780 is it isn't limited to a reference PCB and has more OC headroom. The point being is that the 780 and Titan have basically no performance difference even worth mentioning, so if the Hawaii is as fast as the 780, then an OC version would be a Titan. IMO.
Of course, some games favor specific architectures. Ubisoft/Blizzard games tend to favor nvidia, Square Enix games tend to favor AMD, so that's a wild card. The performance differences will vary depending on specific games.
The only unfortunate thing about this card is that it's too bad it wasn't released 6 months ago. And it's still unfortunate that the frame pacing for eyefinity is a work in progress (when it that being released, anyway). Anyway, nvidia obviously already sold a ton of GTX 700 SKUs since they were the first to the punch.. Either way, though, if the card is 600$ and within the realm of Titan performance, nvidia will likely lower prices. Then everyone can be happy whether they prefer AMD or nvidia, right?