The Sony Playstation VR is back in stock at Amazon! It had been out of stock since about December, enabling scalpers to sell it for $200 or more over the MSRP. But now it's back in stock at its regular $399 MSRP at least for now.
Sony's Playstation VR is still the most affordable desktop VR system. It provides full positional tracking plus motion controls just like the HTC Vive ($799; reviewed here) and Oculus Rift + Touch ($499 + $99; reviewed here), albeit with a much smaller tracking area for standing or seated gameplay (as opposed to roomscale VR).
Despite the more limited hardware, what I like about the PSVR are its games, which tend to be more polished than those for the Vive and arguably even those for the Rift.
The PSVR also recently added capabilities such as native compatibility with YouTube 360 videos and Blu-Ray 3D playback. If you haven't seen it, here's my review of the Playstation VR.
Sony recently announced sales numbers for PSVR and it appears to have the largest number of users among the desktop VR systems, which hopefully will translate into better developer support (i.e. more games). We will be looking for announcements at E3 2017.