Can confirm. I used to regularly miss my shot taking pics of things that were happening briefly because of the delay starting the camera. Now it's very snappy.
Slow speed was never an issue for any of my old android phones. I would have happily continued using my previous phone if the manufacturer bothered to provide security updates. I bought the FP4 at release and expect to use it for at least another 3 years. In my mind that justifies the initial asking price, at the time other android phones with longterm support did not exist.
I have one and have never been in a situation where it's too slow. O must say though that they should have shipped with a decent camera driver to begin with. To me the story reads like this: smartphone manufacturer releases important fix x years too late.