As someone who has used similar tech, I can vouch for the fact that the immersion really is on a completely different level. Vertigo can be especially unsettling. In my demo there was a large hole in the floor and I found myself physically unable to walk over it, despite knowing that it wasn't real.

Edit: on reflection, the sensation was remarkably similar to how it feels when dreaming. Signals from the real world can intrude on your experience (e.g. running into physical objects can cause pain in dreams), but it doesn't break the feeling of immersion. There's that strange mental transition point in a dream where you get dunked under water but realize that you can still breathe; the same thing happens in VR.