I was testing the board for my girlfriend, and noticed the SB does get pretty hot if little to no airflow is on it. With the case side off there was little airflow, and it did get quite warm. But putting the side of my case on (has 4x92mm fans, each flowing about 40 cfm) cooled it down to barely warm at all. One fan was pretty much directly above it, so to speak. NB and VRM both ran fine, too, and no crazy temps to report. Oddly enough, the temps are lower than my wonky 890FXA-UD5 reported. All temps are according to HWMonitor and Everest.
Either way, I have decided to put another 120mm intake fan in the front, and get a GTX460 which is shorter than the 5850.