I switched to them a few months ago, I was previously using duckduckgo (and Google before that). As most of you have probably noticed Google search results have seriously dropped in quality the last few years, but especially in 2023. I'm no longer able to get meaningful results for almost any topic, especially if it's technical, the only results are AI generated (?) / obvious SEO spam websites. It takes me multiple different search terms and clicking through multiple results to find anything semi relevant, and even then it's a shallow article maybe summarising what I'm looking for. Unfortunately DDG seems to be going the same way.
Whereas Kagi reminds me of the 'old' google search. The results are meaningful and relevant, not diluted with pages of generic article results. They also offer a lot of great customisation options like being able to block or boost certain sites in results. They have some built in lists for common filler sites. I can't comment on the AI variation but I hear that's progressing well.
I wouldn't call myself a power user of Kagi, but even then I'm getting far better results than other search engines, definitely worth the price per month.
I'm not affiliated with them in any way, just thought I'd share my anecdotal experience.