I have a datamart design that is fully snowflaked and I don't think it needs to be. The product that will be using the datamart is Cognos Impromptu v7. I'm under the believe that Cognos works better with a star schema vs. a fully snowflaked model. Can any offer an opinion? Thanks.

well dear friend I have used cognos for developing a cube and report too so the best way i felt to use it after designing a star schema and one should always avoid snok flaking as much as possible because that way i think you are again moving back to normalization mode which is strictly not followed in DW design.
Regards,
CogHunt