I've been using it for over a month now and it's great. Search results are on par with Google,if not better. (Probably better, subjectively, since I switched mostly due to getting annoyed daily with worsening results. Ignoring my search terms was especially annoying.) The privacy aspect felt like a bonus, but now I never want to go back.

It requires a login to use and aside from not showing ads, the FAQ makes no promises about not monetizing the per user search history. That's bit of a red flag for me.

This portion of the FAQ: https://kagi.com/faq#privacy

Would seem to address those concerns — if the only money coming in is users paying directly, that would seem to preclude selling the data for further monetization. Or are those known weasel words?