Run into one particular problem - if I Alt-Tab out of the game and then back in, framerates slow to a crawl (2-3/second). So no sneaking out to peek at Task Manager or Afterburner stats.
Run game in Fake Fullscreen. (Yes that is a setting in game, I think it is better known as Borderless Window, those crazy Belgiums...)
Set Task Manager to Always on Top and then you can do both at the same time.
