I have noticed an issue with this update (2015.10.1 on Windows) in LR CC...I seem to be able to outrun the brush pointer. The brush continues to work, but the 2 concentric circles disappear, so I'm not 100% sure where they (and thus the brush) are. In order for them to re-appear I let go of the left mouse button and then re-press the left button. I have 12GB of RAM in my generic I-7 machine, and it seems to happen when I have several other memory hogs running--notably Outlook 2010 and the current version of PS CC. I also (when it happened had 2 browsers open and MS Word 2010).