It is... niche. The display, in spite of butting up against your glasses, is still very small. You're not going to be programming on the command line with one of them (I've tried). It's also not really great as a secondary display either. At least for me, refocusing my eye on the vufine screen and back to the main display isn't faster than switching virtual desktops.

The applications where these do well generally involve large text or video... AR apps like navigation, or watching TV while traveling.

Oooh, I have one. It is really amazing, in that there's really a usable display in a package the size of one's finger.

I've struggled to use it for anything practical, though, because of small issues with the mounting. It isn't quite adjustable enough so it's slightly out of focus. It's a too heavy so it's tilting the glasses and making them fall off if I tilt my head forward. The micro-HDMI cable interferes if I rest my head on anything. So I pretty much have to use it sitting or standing in free space, in which case, why not use a regular monitor?

I wonder if Thunderbolt makes it possible to take another crack at this design without the battery, hugely reducing the weight.