I'm not sure if it's the most recent beta that causes this or not, but I've recently noticed that when the wallpaper changes by itself, sometimes the fade transition effect doesn't happen and it just jumps to the next image as if the transition was turned off. This never seems to happen on manual changes using the hotkey for it, and only happens on occasions when it does it automatically with the interval timer.

EDIT: While I'm at it, I might as well bring this up. For a while now, when my screensaver, that I have Display Fusion controlling, is running, the cores of my computer would often all become overly active. After exiting the screensaver, the cores would settle down again, so it's definitely the screensaver that's affecting it.