How useful are the Garritan Orchestra sounds that come w/ Dimension in Sonar 8.5?

I'm thinking of buying GPO 4, but maybe I should just learn to use the sounds I already have. Can decent arranging or orchestration be done with the basic Garritan sounds in Sonar? Does anyone here use them for anything, like with a real client maybe? I'm just interested to know because I want to learn a little about orchestration. I've been told I should look into doing music for films.