When I bent my mainshaft I polished the replacment I installed and yeah, it is very shiny. That's not why I did it though. The real advantage of a polished shaft is that everything still fits tight, but is much easier to disassemble if needed for repair. I got the idea after I had such a hard time seperating the original mainshaft from the main gear with a hammer and punch. I even had problems getting it through the upper bearing.

Pilotlight polishing your new mainshaft will go a long way towards ease of repairs down the road. Plus it's shiny...oooo