It is night and day difference, my DK2 gave me nausea so bad that I couldn’t even look at the headset without feeling nausea and I was developing on it so had to keep going. It was an amazing yet horrible experience all at once lol. Even thinking about it gives me shudders. But then you get your sea legs and things like moving outside tracking volumes seem to have less long term effect. So although 80Hz is not ideal for new VR users, people that already have and use VR will hopefully not experience the same degree of nausea.
The testing units will of course reveal this in the next month or so.
Our ability to detect Hz difference is individual but is also a logarithmic scale rather than linear. The higher you go the less difference it starts to make. e,g. 60Hz vs 75Hz is a notable difference. 75Hz to 100Hz is an improvement but not as much as you would think. 100Hz to 120Hz is to me almost no difference. Of course if you make the gaps bigger then you get to see it again like 75Hz to 144Hz but we are not talking about big difference here. 10Hz difference at the higher end may not be very noticeable imo. I hope not anyway.