This is fantastic to hear. I've actually been trying this with smartphones. I have a few that I've made tolerable by gradual increases in exposure. If might ask, how old are you? I think the reason these adaptions are possible is growth of new brain cells to better process flickering / unstable / otherwise bad imagery. Now that I am in my 30s I find it takes a lot more time to adjust to a new device compared to my 20s - which correlates to a slow down in new brain cell growth as we age.
Were your headaches the normal kind or migraines? (migraines also feature nausea and sometimes visual changes)