I installed the Windows 10 Mobile version on my Lumia 950 XL this morning (10 November 2016).
It was crashing a few seconds after opening the app. Could not even enter an email address to login.
There was an update in the Windows store a few hours later. The above issue was resolved.
However, it runs substantially slower on my on my Lumia 950 XL when compared to a Samsung Galaxy S7 and an iPhone 6S.
There does not appear to be a swipe function (left to right) to close a PowerApps 'app' (like there is on Android or iOS). When used on a Surface Pro 3, I can swipe down from the top of the screen to bring up the Exit button, clicking this takes you back to the the main menu (of course this would not work on the phone as a swipe down it would bring up the phone settings). As such the only way to exit an 'app' is to click the back button, but this actually cycles through every screen you have been in until you are back at the main menu (e.g., if you have gone into 20 different screens in that session, clicking the back button will take you through all 20 screens before you get to the main menu).