[fritsch]

Also noticed that anytime I seek forwards/backwards during playback, the screen will go black for a split-second, I think to display the buffering overlay. This is a little jarring, especially when it happens on locally stored files, maybe it should only appear after some small delay?

I also have this same problem when I skip or switch to play from FF. Black flash after each skip. Not sure when it started, I was using #0504 before and it didn't have this problem.     

Tested this and #0504 is the last build that is free from the black flash. All builds after that have the same problem. Using Intel Haswell graphics.
Build #0505 added this change, is that the cause for this problem:
VideoPlayer: flush renderManager when hiding video (PR:13824, 2 commits, 1 file changed) 

 That's by intention ... so that for livetv the stream starts with the picture itself and that not the old pic stays on screen.

For the Limited GUI issue: https://github.com/xbmc/xbmc/pull/13934