I've been using Brave Search for the last few years. It returns much less crap than Google Search.
They introduced the AI summaries about 9 (?) months ago. My experience has been generally favorable. It's accurate about 70% of the time, partially accurate 28% of the time, and wholly wrong 2% of the time. I tend to ask it technical questions and the responses that are incorrect are usually deprecated/outdated. It doesn't have a sense of time. Last I checked, it was using the Llama LLM.
Overall it has saved me time from clicking on a bunch of results trying to find the pertinent information. Often it helps me to re-phrase the search so I can get more accurate results. I don't have high expectations for AI and so I take its responses with a good dose of skepticism.
I don't use the Brave browser.