Used the R50 outside in Florida. High 70's temperature and sunny. After about an hour, the device refused to see balls placed in the hitting area and the screen was unresponsive. The screen was hot to the touch. Took it inside for a while and tried again and it worked as expected.
Seems odd that a device intended for use like this failed in these comfortable conditions. Even worse, it did it without (unlike, say an iPad or iPhone) a warning.