I has a quick 5 minutes on one in Andertons last Friday, my first time with fanned frets.
I felt comfortable with the frets after a few seconds. I didn't have to acclimatise, and I was pleasantly surprised to not be playing two frets higher up the neck than I wanted, which has happened when I've tried headless basses before.
It felt comfortable, but I hardly ever play sitting down, so I'd like to see how it feels on a strap.
The sound was quite clean and hifi, which I like, but I found the tuners quite difficult to use.
It's definitely worth trying one if you can.