I used 10166 on a 535 dual sim, as a temporary daily driver during holidays. It was really OK, but every once in a while, it would reboot itself (or force me to reboot), and I had to check if notifications (SMS ones) were ok after each reboot.
I consider that this hit&miss notifications, restarts, etc. are acceptable, as a daily driver, when on holidays, but back home, I'm still using my 1020 with WP8.1. It's not stable enough, or rather, reliable enough, to have me insert my SIM in the 535 running W10M. Not at this stage.
Besides, the 1020 will never see any preview program (insider, preview for developers), etc. : it's my real daily driver and above all, I don't want to mess with my main camera ^_^