In a market where "Early Access" can last for years, SteamVR for Windows Mixed Reality spent a remarkably short time there at only about five months. This week, in conjunction with Microsoft's announcement of its Windows 10 April 2018 Update, Steam announced that the program was ready for prime time.
For those unfamiliar with it, Early Access is the equivalent of a beta for games. Early Access differs from betas because you frequently have to pay for the privilege.
If you tried out the early versions and were disappointed, Steam says that the beta cycle "resulted in significantly improved performance and stability, added haptic feedback for motion controllers, and improved how motion controllers appear in SteamVR." It also says there are now 422 Steam games which officially support it. Hopefully that means there's going to be a big sale on them soon.