Note: Threading is NOT just about performance - in fact I never used the performance / speed-up once in this thread.
What threading allows for is smooth / stutterless rendering - being able to stream in worlds is a huge bonus. It's a complicated issue because you have to deal with half-loaded resources and other bad conditions without barfing. But the end results are games that can be very dynamic and large.
It was mentioned in a different thread recently:
http://www.ogre3d.org/phpBB2/viewtopic. ... 6f4e2718c6