Until the mobile experiences have a quality 6dof and motion controls, they have almost no appeal to me.
As far as more immersive experience, I probably could afford to build a new computer and get a proper VR system rigged up but the cost involved vastly exceeds the level of appeal it has to me. The image quality is definitely at a level where it it probably already is pretty great, mind!
These platforms should drop the VR moniker - they are 360 stereoscopic ten day wonders and little more.
Go also has a Snapdragon 821 for ONLY VR. The GearVR was sharing resources with a ton of other garbage background processes that Go doesn't need to worry about. And the thermal performance is also way better.
Finally, you can get Oculus Go to run at 72Hz which is a way more comfortable experience than GearVR.
So you get a lot more than your phone can give you for 25% of the cost.
As you say, it's a good deal given the modest price point.
Sadly the Snapdragon is woefully underspecced in it's video decode capability - tops out at 4K which is less than ideal - 5K HEVC are already popular and a noticeable improvement for VR video.