Hi all! Escape was removed when we added in Simulate and Play in VR mode, as that key is used to exit those modes. I’m currently working on a change where the escape key will leave VR mode if you’re not simulating or playing, though.
For now, in 4.16, Alt+` will exit VR mode. In 4.17 and beyond though, it’ll be Alt+V for VR Mode. 
In both cases though, you can remap the keybinding in Editor Preferences. If for some reason the key combo isn’t working for you, make sure the preview window has focus by clicking on it.
Thanks for trying out VR Mode, and hope this helps with your workflows!