With Kagi, I think I've gone back to Google a couple of times in the early period. Then not once, since last winter. On browsers where I'm not logged onto Kagi I've gone from Google to my primary browser with Kagi multiple times. I can't really tell if Kagi is good or bad, objectively, but in relative terms it's very good. Most importantly, it's quite invisible, doesn't have irritating things to fight with, and the first two pagefuls aren't sponsored ads. It's tool-like and it certainly gives the feel of 2000's Google Search.
I don't know if I'm a fan but I still also have no reason to stop using Kagi. I like the simple concept. And I think paying for search is a good proposition because it turns the odds to my favour: the company can succeed by making me happy instead of using me to make advertisers happy.
I guess it's down to you how much you value web search. Kagi does have an AI tool as well, but I didn't use this and don't use AI search anyway, so can't comment on how it compares.
The search results are much more relevant, there are no ads or hallucinated BS AI summaries at the top, and you're not giving Google your data (and money) to further enshittify the world.
There are features I haven't tried yet so can't speak to them, but that's my very general take on the default kagi experience.
There was also an instance recently where I was helping out a coworker get set up with something. I had done it earlier in the day, so I told him something like "type in $SEARCH_TERM, then go to the first page and copy the commands from there". He put it into Google, couldn't find the right result, tried a few variations, still couldn't find it. I pulled Kagi up on my phone, searched the same term, and slacked him the page while he was still looking around on Google.
obviously neither of us have peeked under the hood at google and kati’s source code, so hard to tell for certain at face value.