Basic functionality works, but some websites become completely unreadable. Also, it doesn't really turn "off" correctly, and I have trouble getting it to ignore certain websites. For example, duckduckgo has a great built-in dark mode, which I always use. However, this app doesn't think I should use dark mode during the day and overrides my settings, even when ostensibly "off". Super annoying!!! No way to tell it to just ignore duckduckgo.

Barely better than the free ones, nothing that impressive, too expensive in my opinion when you know what you can get for free. Also doesn't let me try the lite version before having the trial, it feels like it's just meant to mess with people when the trial ends really.
Basically, there was an attempt to make something great, but it feels malicious and I hate that.

looks good, but slows down firefox until it's unusable because my CPU (i7-6600U) is utilized at 90-100%

Extension payante !!!

as many said slowed down and made it unusable on several web sites, I thought it was good on Facebook too until I got to my home computer and it was awful and it is a far better equipped computer... I'll wait for an update or a built-in solution. (on Facebook it turns all the emoji black)