Installing hello.v will show an FPS counter if you press CTRL+F in game. It is a bit annoying to keep permanently in game however, so use it when you want to see FPS without obscuring your view. Alternatively, pressing CTRL-F while in game will show the normal FPS counter in the Desktop mirror of the game - that is accurate to the VR FPS and not the desktop - but it only shows 45 if ASW is working and 90 if it isn't.