I have a Lumia 535 Dual Sim with Windows 10 Mobile Update via Upgrade Advisor and currently having an issue with the Navigation Bar. I've seen the same issues with Lumia 535s running the Technical Preview since last year. Now Windows 10 Mobile is an update for non-Insiders, yet the problem still persists. One example is Temple Run 2 and the Navigation Bar overlaps the app. When hiding the Navigation Bar, the bottom part of the app remains untouchable and cannot be interacted with. On the other hand, Temple Run 2 and the Windows 10 Navigation Bar work just fine on the Nokia Lumia 730 Dual Sim with Windows 10 Mobile Update via Upgrade Advisor. I think this is an issue relating to smaller resolutions like of the Lumia 535. AND the Navigation Bar does not respond to swiping up to appear on some apps. One app is Dumb Ways to Die 2 where I had to swipe down the Action Centre, tap All Settings, to get out of the app.
(I'm posting this as my feedback. My experience with Windows 10 Mobile has been somewhat great.)
My problem with the Navigation Bar works like this: http://answers.microsoft.com/en-us/insider/forum/insider_wintp-insider_perf/problem-with-navigation-bar-on-lumia-535/fd11de26-9e7c-4cb4-ab7d-97ac15194f20?auth=1