I finally got to try my inov8 running jacket in a proper downpour today. Just gentle walking and standing around in a field. I was wearing a cotton t-shirt underneath, nothing technical.
It felt cold and I thought I was getting wet. At least it wasn't hot a sweaty despite the hot weather between the downpour and the next lesser shower.
On taking the jacket off indoors, there was a very clear line. Shirts and bottom of t-shirt were drenched, still dripping in fact. Above the line was totally dry! Now, the line was higher than the bottom edge of the jacket due to wicking upwards, but it was a clear difference.
I'm still only going to carry it in the mountains when there is no expectation of rain, but it gives me more confidence in it.