So, 3dfile.io supports Autodesk Inventor *and* Solidworks files right out of the box. Sketchfab, on the other hand, only does these dumb tessellated formats that all the 3D printing people use.
Note that the body appearances in this viewer actually aren't what I have them as in Inventor; apparently 3dfile.io is applying some sort of changes to the file when I upload it. Regardless, not having to export as a different file format is great. I don't see how I'll be using Sketchfab at all anymore.
Oh. Also, I modeled a can. Pretty neat, huh?