Looks like most people won't notice any affect (under windows), it will mostly be an issue for servers. Tests seem to confirm that only those using very high IOP rate bound applications (like your high frequency trading software previously mentioned) would see any affects at all.
https://www.techspot.com/article/1554-meltdown-flaw-cpu-performance-windows/
Whew! So no need to upgrade, then. Just moving up from Win 3.0 was painful enough.