I'm interested in knowing the primary determinants in choosing 8-bit versus 32-bit projects. I know that 32-bit projects are a bigger burden on the processor and are therefore slower. I also understand that 32-bit stands up better when color grading filters are used. What do you use to determine which mode you choose to create any given project?

As you mentioned, if you are doing lots of color change or using gradients of colors, it can be useful. If you just drop DV on the timeline and render to DV, you won't see a gain. If you're using photos, you may see some improvements. Best way to determine if it will help in YOUR situation is to try it both ways.

Not may people know about this:

Color spaces and levels in Sony Vegas 9 (http://www.glennchan.info/articles/vegas/v8color/vegas-9-levels.htm)