Earlier this year I looked seriously at upgrading to either a preowned Tyros 5, or a new Genos, from the S770.
Now if money were not a consideration, of course I would have bought Genos. But while I could have done that, I don't have quite enough money in the bank to not have to think about it carefully first. Pricewise, the cost to change to the Tyros was less than half the cost to change to the Genos. So I had to look carefully at the differences between them, to see whether I felt I could justify the higher price.
My local dealer had both Genos and preowned Tyros 5 on display so I spent some time with them both. For me, personally, I could not find a compelling reason for the Genos over the Tyros. The sound on Genos may be a little clearer, but I think the main difference between the two is the Genos touch screen and live control section. This wasn't a big deal for me since I'm not a big fan of touch screens, and I bought an inexpensive MIDI controller with knobs and sliders which can do the parts of Live Control that I want to (reverb depth, filter, resonance). I only use it at home, so weight wasn't an issue, and the deal included the 1GB flash memory.
So I went with Tyros 5-76, because there was enough improvement from S770, and I felt the Genos improvements over that were marginal to me.
Just to be clear, I am not Genos bashing, I thought Genos was a beautiful instrument - in my position I could not justify the higher price, but I don't criticise anyone who can. Maybe when Genos v2 comes out I will trade my T5 to a Genos v1 ...