I've taken NanoFlashes up into the arctic and down into the Arizona Desert in the summer. The only time I ever had an issue was when I had an intermittent HDMI cable, The NanoFlash did warn me of this, but I continued trying to shoot (I had no other cable) and this did eventually cause some corrupted files.

So am I happy with the reliability? Yes completely, I used to have so many problems with tape in the environments I shoot in, but the NanoFlash has been a dream to use.