My personal experience.
So after building my Kabylake Core i3 7100 system, I got everything ready to enable Optane Memory but did not enable it. I just wanted to see the difference. I used the Seagate 2TB HDD for a while. It's not a SSHD.
This post isn't about how much it made my system boot faster or my games/applications load faster. I just want to show you a very interesting scenario why fast storage can make a difference.
Seagate 2TB 7200RPM drive only: There's a flash game I play that takes immense CPU usage in Firefox. CPU utilization goes to 90%+ when the game is playing and it takes ages to load. It makes you question how uncaring the game developer is regarding performance but that's not the point.
You'd think 90%+ CPU usage means its hopeless. However I remembered that on my Core i7 3517U Ultrabook that it wasn't that slow, and it also had Windows 10 installed. I immediately thought it was maybe due to the slow storage and its causing lot of stalled operations on the CPU. Also, Firefox sucks just for this game and Chrome performs better. I normally used Chrome on my laptop. The problem is I have compatibility problems on Chrome. Some servers don't load properly.
Enter Optane Memory. With it enabled, it reduces CPU utilization to less than 15%. That's right. CPU utilization graphs are misleading. My CPU was executing stalled instructions, because the drive was too slow for that game on Firefox. It's still slower than Chrome, but its much faster. It doesn't stop other programs in the background. The reason I suspected CPU stalled instructions likely due to slow I/O is because I read this short while ago: CPU Utilization is Wrong