In my experience the transition from normal FreeSync Range to frame doubling has been the same transition I see from 60 FPS to 59 FPS, or any other FPS number inside the FreeSync Range, it looks natural, just like if it was part of the Native FreeSync Range, stuttering is a non Issue at any Frame Rate.
There's one thing though, when going above 144 FPS in games like Battlefield 4 or any game really, there's this small increase in brightness for a fraction of a second, maybe lasting around 5 Milliseconds or so (Little over half a frame), it always happen when you get out of the FreeSync Range above 144 FPS, and if you oscillate around 143 and 145 FPS then you'll see it each time you get in and out the FreeSync Range, although it doesn't impact performance or any other aspect of anyone's gaming experience, I would say it's a minor visual imperfection.
You can always use Vsync in Game to cap the Framerate to 144 FPS so this never happens, Vsync Plus FreeSync works wonders, if you don't already know Vsync can be used on top of FreeSync so both combined can deliver an incredible experience, whenever at 144 FPS capped Vsync takes over with No Extra Input lag, the Vsync Input lag comes when you dip below 144 FPS to 143 FPS, but when this happens FreeSync comes in replacing Vsync, thus eliminating any Input Lag associated with Vsync, this happens automatically whenever you enable Vsync while having FreeSync enabled.
Also you can use AMD's Frame Rate Control to cap the FPS to 143 FPS, but for some reason it's not as solid as capping 60 FPS, when you use this tool to cap at 60 FPS it really caps the frame rate dead on at 60 FPS with no Variance at all, but with higher refresh rate (Beyond 120) it's more like a target number, if you set it to 143 FPS in some games it'll go varying from 140 to 150 FPS, in others is more precise, going from 142 to 145.
Edited by Dargonplay - 3/27/16 at 9:00pm