Honestly, if I was to buy a new computer, this is the first thing I would download.
Although Apple and Google have integrated blue light filters into their operating systems, they still haven't matched the capabilities that f.lux offers. f.lux gives you more control over the filter strength and once setup, you don't need to touch.
I have been using this since it first showed up on Product Hunt. It's probably my most used 'app' even though I barely ever interact with it. Once I found my optimal settings, I don't think I've opened the app itself more than a handful of times. It works as advertised most of the time. The only time I've had issues is when using it on external displays with Linux. Since it's my secondary device, it's not been much of a problem though.