Optically very different from the Voigtländer 2/40 Ultron SL/SLII (Planar / double Gauss) or the Nikon 2,8/45 P or GN (Tessars)...
Why not a metal mount ? To cut costs ? Should'nt cost much more...
Next compact pancake after 2/40 and 2,8/28 ? A little tele/portrait lens (a new 2,5/105 or 2,8/100 E in Z mount ?)