The Eva interface is pretty cool, but it is not worth what I paid for it. I would recommend people look for other options or maybe wait for something better to come out.
Not sure when something better or more interesting is likely to come out in terms of UI --- the days of pen-centric UI experimentation seem to be over (I miss Go Corp.'s PenPoint, kind of wish I'd bought a Momenta, and these days even look back on Windows for Pen Computing and Windows XP Tablet PC Edition w/ fondness) --- arguably, it's been quite downhill since Microsoft crippled styluses as a dumbed-down 11th touch input for scrolling in Fall Creators Update. Windows 11 is barely usable, but I still have to keep the Settings App open so I can toggle back-and-forth between using the stylus as a mouse or no, and the only browser which supports disabling scrolling w/ a stylus is Firefox, so I have to remember a specific Github page which has the instructions for toggling that UI setting.