Not sure if this is a beta issue or not, but I noticed recently that switching to and from Reading View (F11) takes sometimes up to one minute. As before, it does visual gymnastics switching into an odd-sized smaller window first before finally switching to full screen. Many times (starting happening yesterday I think) it will just stay in the odd-sized smaller window without any way to maximize it to full screen (double-clicking on title bar doesn't work).
Anyone seeing this problem? I'm running Windows 8.1 with an external LCD monitor. This has happened to me on both the laptop/netbook screen itself and on the big monitor.
Peter