The D750 does look a good camera. I'm glad that I waited & didn't buy the D610 last month, if I had, I'd be feeling pretty sick now. The D750 price is coming in at only a few hundred more than the D610. It was obvious to me that something was going to happen to affect the D610 due to the price discounting & offers on the D610 last month. I took this to mean a D620, but the D750 does seem to be an upgrade on the range.
For specification, the D750 sits a lot better & if I owned, say a D7100, I really would feel that the D750 was an upgrade, whereas the D610 looked one step forward & one step back to me. As a prospective buyer (I was specifically waiting for the D750), I am impressed with the new model & would have bought one - had I not talked myself already into the D810. The better AF, metering & rear LCD (on the D750) is enough to make it sell well in my opinion & I hope that it improves Nikon's sales. In the end, my preference for landscapes & macro has helped me decide on the D810 mainly due to the ISO 64 & 36mp. I am very glad that I waited & very thankful to the forum members for the high level of quality advice given over the past month.