"the estimate of $1599 seems a bit too far-fetched"
I think it's safe to say that pre-release price estimates for these sorts of things are rarely accurate, and often inflated. Pricing around the $1000 area seems far more likely, although I agree that a sub $1000 price point would be more reasonable. $800ish? ...please? ...nope.
I'm really not sure why there's been such astonishment at the higher clock speeds. Like I've said before, I would be surprised if the Geforce Titan had the same or similar clocks as its Tesla counterpart. Geforce cards have traditionally been clocked higher than their Tesla or Quadro equivalent, and as far as I've seen there's been no evidence to suggest that the situation would be any different this time around, which is why I've been skeptical of the rumored specs for the card up til now. Everything was exactly the same as the Tesla K20X. I think someone either got confused or simply didn't know what they were talking about, and posted the specs for the Tesla K20X as the Geforce Titan.
I'm also a little skeptical about this new 512-bit memory interface rumor. If I'm not mistaken that would require a revision of the memory controller on the GPU, and it seems unlikely that Nvidia would revise GK110 specifically for their Geforce cards. In other words, I don't think it's possible to simply strap an existing GK110, designed around a 384-bit memory interface, to a 512-bit interface and realize the additional bandwidth. The memory capacity is another clue that seems to further contradict this story, which is still rumored to be 6GB. If it were a 512-bit interface, I would expect to see something more like 4 or 8GB on the card.