For those who are unclear as to what early access means, Steam describes it by saying, “This Early Access game is not complete and may or may not change further. If you are not excited to play this game in its current state, then you should wait to see if the game progresses further in development.”
Basically you could think of early access as beta, where the game is mostly playable, but there might be some features that have yet to be fully implemented, and there could be glitches during the gameplay which should be expected. It should also not be taken as the final version of the game as the final version will obviously address certain issues, and may or may not remove features as well.
That being said, its release date is set for October so if you’d rather not play the early access version, you’ve got some waiting to do. As for non-HTC Vive owners, fret not as the developers are planning an Oculus Rift version as well.