I've been using it since it was called FancyCache (many, many years ago), and have never had it cause any instability in my systems (I run it on multiple servers/workstations/gaming machines now).
I'd recommend Primocache to anyone looking to speedup their notebook, PC or workstation in general. It takes some tweaking but once settled down you could see, experience and even benchmark the differences.
I used PrimoCache with Intel Optane on AM2 platform and Win7-64-sp1 to show that caching may be really fast on old systems. I also tried your Ramdrive and found it super for browsers profiles.
I noticed great improvement in VMs load time, especially when a few were started in parallel. My host machine didn't "chok" like it used to without the cache.
Your software fixed the bottleneck in my mother's PC that I had been attempting to fix for a long time. PrimoCache software worked like magic and her PC finally operated at a speed I could be satisfied with.
I have been following your software for years, I used during the Beta period. It since I know is a great piece of software.