Are you using any of these? (for retopology) I ask because I want only seasoned, regular users. I can also read forums and hearsay. Just for the record I have tried both Topogun and 3DCoat, (and zBrush too). But I have not tried Polyboost so if anyone has tried that I will be extremly interested.

Edit: I take it for granted that automatic conversion is not possible but a combination of tools and 'hands on'.