Got my first Linux ARMv8 (64 bit, as opposed to the ARMv7 instruction set which is 32 bit) machine (manufacturer link):
Here a graph CPU load over CPU temperature:
As you can see, the heat sink does it job quite well (room temperature was about 19°C). The case gets warm, but not hot (below 50°C I’d estimate).
The whole thing is powered via micro-USB (+5V) and needs about 400mA when idle and about 100mA extra per 100% busy core running at 1.3GHz.