If you want the same result as in your image from 2.49 ( with ngons but no tris) you need no addon. Just use limited dissolve. Go to edit mode and select all faces the go to the mesh menu->clean up-> limited dissolve.
Weird. The importer addon should convert all ngons to tris. This is because blender cannot support keyhole ngons, which LW has, and there is no (that I could find) way of isolation only the keyhole ngons, so all ngons are converted.
I have had no feedback on this, I was thinking of keeping the current action as the default, but allow the ngon triangulation to be disabled, with the keyhole ngons glitches, which is what used to be the case.