I actually also use Maya and am thinking of something that might also cut down my render times but I figured to focus on SL here (though I'm sure a lot of you also have good experience with 3D rendering as well).
In any case, I grabbed open hardware monitor as suggested and did some tests with puzzling (to me) results.
The scene is heavy mesh buildings and objects and about 15 - 20 visible avatars, running the latest Firestorm viewer.
FPS: 8
CPU Load: Combined 16% with 40% max spike on initial scene load, pretty evenly distributed over all 4 cores
Memory Usage: 6GB of 12GB, 50%
GPU Load: 50%
GPU Memory Use: 93% (of 2GB)
Now here's another interesting piece of data. This scene is much simpler. 2 Avis, skybox with few mesh objects
FPS: 50
CPU Load: 9% - 30%
Memory Usage: 4.3GB of 12GB, 35%
GPU Load: 95%
GPU Memory Use: 52% (of 2GB)
A couple of interesting things there that surprised me. Looks like in the complex low FPS scene the CPU and GPU aren't working that hard but still very low FPS and the GPU memory is near maxed out. In the simple scene the GPU is working hard but with low GPU memory use.
It's looking like somehow the bottleneck is the GPU memory. Possibly the slow FPS is coming from the textures being swapped in and out of graphics memory. It's not surprising with the way people make things in SL (so many non-optimized textures) that a lot of GPU memory would be eaten up, what is surprising is that I thought SL could only take advantage of 512 megs of it, so how is my 2GB card maxing out?
Anyone have any insight on this? It's got me really curious now.