Hey bwiklund -
When you say just return 0 or (0,0,0) are you referring to Cascade or the Material Editor? The viewports for each of those editors do not preview World Space Nodes as there is no reference to pull from and they will always return a 0 value. You should however be able to add the particle system to your level and see the effects of the nodes there. If you can let me know what exactly you are trying to do I can run a more specific test for you.
Thank You
Eric Ketchum