Since installing 10.12.4 beta 1, I'm seeing long delays opening files, which seem to be caused by the XprotectService scanning files on open. Files that used to open immediately are now taking minutes(!) to open, with the "Verifying (file name)" dialogue parked in the middle of the screen. Seems to be particularly bad with large video files in .mkv format, although it's affecting other file types as well. While trying to open files, XprotectService is taking up 40% - 50% of available CPU time.
Anyone else seeing this, and is there a way to work around or completely disable Xprotect?