Is Qi / wireless charging safe? Heightened temperature not an issue? (Nexus 7)
I am charging the device regularly and checked with a system monitoring app the temperatures, that I reached. It was never more than 33 degree Celsius, while charging or after charging, still laying on the charger. 

This is to be considered a completely normal temperature. Just today I was out with the tablet  on the sun and I reached more than 40 degree Celsius, just because of the sun, so I wouldn't really consider charging with Qi an issue.