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I'm always amazed at how well WebGL works - I used to think that 3D intensive applications would be one thing that would/could not be converted from desktop app to web app.
I'm not really sure I see the point of the original post though, since it is just a viewer and not an editor. tinkercad's ability to import, edit, and export stl is extremely compelling.
(spin the model around until you're looking at the back of his head, watch how his face always looks like it's looking straight at you, i believe this is a known psychological effect but some quick googling didn't turn up any results)