Place your hands on both sides of your head. That is about what it is like. You have some peripheral, but not much.
It is not like looking at 2-miniscreens. It really immersive, and even knowing I was in VR, I have tried to lean against a virtual object, had acrophobia, and walked into a wall or two. (HTC Vive).
I used the DK2 before the vive, and even that was pretty good, but lacking the ability of room scale and controllers, you still felt tethered more so than the vive.
It is NOT underwhelming. It is pretty damn awesome when people do it right. The trick to remember is that this is the first salvo of VR. So it is really awesome, and it is going to get more awesome in the near future. All the problems with VR you can find in discussions, and you can never really grasp it, till you try it. It is like explaining 1080p to a person who has only ever seen 320.
So yeah.. question answered I hope? Here is the question I like to ask myself..
Q: I've spent $800 on the HTC Vive.. do I regret it?
A: Nope! Not at all!