I tried using one of the existing converters in Blender for XML-type stuff, namely the XGL format, but for our project found that we had to abandon it immediately as it bloated the files to sizes completely unacceptable.
I guess it all depends on what formats you are wokring with, but the .py exporter for .obj files works pretty well for me. I have had a few problems with the .3ds exporter as it doesn't seem to want to include material settings or textures, but then again it could just be me

But generally Blender is quite good IMO - its a nasty learning curve in the beginning, but once you start getting over the hump there's a lot of power there