I'm having some graphic driver issues on my SP3 since the update. I've only encountered it so far playing the Microsoft Solitaire Collection, the graphics driver will crash (it says it's a problem with the Windows 8 graphic driver...). The game freezes and eventually I have to reboot the machine. Not sure what state of the art in upgrading/downgrading video drivers is these days.
What is the latest insider build, 10585? If so, is that TH2? Anything newer than that? Easily a dozen and a half builds on my SP3, I've stayed at RTM on my new SP4 but am ready to jump back in as this business of not coming back from connected standby when not plugged in is driving me nuts.
Not many noticeable changes cited yet. OneCore being firmed up.
However, the bug where progress bars were not being displayed while copying or deleting files from File Explorer or the Recycle Bin is fixed.