As a Kagi subscriber, I find this to be mostly useful. I'd say I do about 50% standard Kagi searches, 50% Kagi assistant searches/conversations. This new ability to change the level of "research" performed can be genuinely useful in certain contexts. That said, I probably expect to use this new "research assistant" once or twice a month.
I have yet to understand when to use `?` versus `!quick`. The former is much less disruptive since it's very fast and displays an answer above the normal search results. And I haven't played with them enough to know what kinds of things `!quick` is meaningfully better at than `?`.
I've already used the Research assistant half a dozen times today and am super happy with the outcomes. It does seem to be more trigger happy with doing multiple searches based on information it found in earlier results, and I've found the resulting output to be reasonably accurate. Some models in particular seem to never want to do more than one search, and you can tell the output in those cases is often not very useful if the sources partially contradict each other or don't provide enough detail. The best I've found to avoid this is o3 pro, but o3 pro is very slow and expensive. If the Research assistant gets 85% of the results in half the time as o3 pro...
Same, I'm quite happy with it. I first subscribed because I was fed up with the promoted results in Google but now I find their assistant searches actually useful too.