No heat issues whatsoever. Running AIDA64 CPU stress test and FurMark GPU stress test at the same time yielded max temps of 60°C on the CPU and 62°C on the GPU. Ambient was ~20-22°C.
CPU overclocked easily to a stable 4.5GHz with no voltage adjustment. GPU overclocked to a stable 2.11GHz.
As you can see in the pictures, I had to make a small notch in the case to fit the power cables for the 1080 FTW.