Seriously, if you want a real experience then turn off the PC, go outside and DO IT.
Ah, the "it's not everything so it's nothing" attack. If you happen to live in the upper northeast, I could see this being a helpful part of one's winter-exercise regimen. Or inner cities. Or anywhere where easily - accessible mountain bike trails aren't accessible.
And the truth is, for many of us, something like a MTB trip to Moab would be really cool, but it's not quite high enough against competing options. It'd be awesome to experience some of that scenery.
Lastly, for anyone naysaying the technology... give it time. VR is in its infancy, and in some not too distant future, it will be indistinguishable from the real thing.