if you want to see one of the most visable errors caused by the other converters, pass a ship that is between you and a local star, watch the sun glare, it will pop in and out of exsistance through the hull of the ship. you will also likely be able to fly through these sections especaly if you are in a model converted by these programs as well. also PCS does a better (though it copuld still be improved) job of calculateing mass, most other programs simply give each ship an arbitrary amount (ie 500, for everything from a 1 meter missle to a 7 km supper jug).
non-planer polys are less of an issue with FSO, becase FSO (int HTL mode) triangulates everything. it is however still an issue when converting, becase it's hard to tell wich side of a poly another poly is on when the verts of that first polly arn't all on the same side. this is allso the reason why intersecting polys are very very bad, it's hard to tell wich side a poly another poly is on when they go through each other.
Kaz, I had an idea for fixing the problems assosiated with geocentric pollys, you could simply place any two polys that have the same center into the same leaf of the BSP tree, if you look at the data produced by the V converter, you'll find that there are a lot of polygons held in the same leaf, and interesting thing about BSP trees it is sometimes faster to simply test a few polygons than to recurse everything down to an individual poly.
from the sound of it ShadowPuppet, it sounded like you were takeing a model directly from lightwave and converting it to cob without useing truespace, it's hard enough to find a converter that truespace it's self will accept, it is unreasonable to require suport of half complyant file standards of every dolt in the world who wants to make a cob exporter, Kaz only suports files saved by truespace, if you are still haveing issues with getting your model converted maybe you should try a diferent cob exporter, as mentioned 3DE has a proven track record, you should try that, but still open and save from truespace.