For me 8.90.5 from a Samsung EVO+ on a Tanix TX7 is running pretty well, so smooth and no stuttering, even Live TV on HD. I stream sat from a Vu+ and play it with Enigma2 PVR on the TX7, and all is OK.
Only issue I have is the "slowmotion" caused randomly with Hyperion, but it's a common problem on all s905 boxes, and seems that the problem is from Amlogic Kernel and drivers, nothing to do by devs.
Thanks for your efforts!