We having been using these launchpads during theatershows to start samples, music, etc. This weekend we had a few shows in daylight on festivals. Shows were tent-based, not in direct sun-light. Environment was ventilated but still warm.
In daylight the LEDs were barely visible making the device hard to use. We solved it with stickers on the keys. Not ideal, but it worked.
After 7 minutes in the first show the Launchpad went black. After a few minutes it came back on, but cycled through all kinds of programs. This was probably due to warmth, although location was decently ventilated and it was out of direct sun. The environment was warm though. I replicated this problem the next day during a tech-rehearsal, again out of direct sunlight in a ventilated spot in a warm tent.
Having said that: for indoors it's an absolute dream. Rock-solid, great build quality, small, no cables and connectors.