I can tell you that I’ve been using Kagi for a few months and it hasn’t been life changing or anything. But I would say that it has been useful enough to keep around. I honestly like the info dense layout over the other search sites, and I use the ability to push down or block sites entirely so I don’t see the spam sites I don’t want to see. Also, “quick answers” is actually pretty useful sometimes when I don’t want to click on any of the search results. Plus, with the $10 sub, you get unlimited uses of the summarizer, which has been great for arxiv papers.
I wouldn’t say it’s for everyone and I don’t know if there’s astroturfing going on, but it’s been useful enough for me to keep paying the $10 a month
I will never forgive excel for automatically converting all of my dates to some weird ass format, or stripping single quotes randomly, or something other BS that they do for no reason