Not happy at all with Lightroom 4. I am running the 4.1 RC2 version. My screen is showing a lightroom error that indicates "Invalid numeric entry. a number between - 1.#J and 1.#J is required. Last value inserted" I can not turn it off and I cannot close Lightroom. This has been a disasterous update. Still very unstable and slow in resonding to adjustments. I get frequent "Not Responding" with a show of gray instead of the image and then a flash to a white screen with it coming back to show the display. Wasting so much time in waiting for the program to respond properly.