As an example, on a scene I was working on some weeks ago,(1247MB in Octane), the export time was 3 min 40s when exporting from blender 2.49b with the old script, and 7 min 52 when exporting from Blender 2.59 with the unsupported Blender plugin v1 !

As I said in the topic of previous version, I have noticed something weird thanks to the ressource manager of Windows 7 : During the export process, at a moment, the exporter for 2.59 puts in cache around 4GB of data. It is weird, because there is still half of my RAM amount available at this moment (around 4GB of the 8GB total).
I don't know it this information can help to find out what slows down the exporter.
French Blender user - CPU : intel Quad QX9650 at 3GHz - 8GB of RAM - Windows 7 Pro 64 bits. Display GPU : GeForce GTX 480 (2 Samsung 2443BW-1920x1600 monitors). External GPUs : two EVGA GTX 580 3GB in a Cubix GPU-Xpander Pro 2. NVidia Driver : 368.22.