If you still have CS3, and a machine that will still run it, I wouldn't bother upgrading. There were some nice updates in CS5, if I recall. 5.5 was buggy.
I have both CS6 and the Cloud versions, and use CS6 wherever possible. Rarely do I need the Cloud. There is supposed to be a better silhouette tool in the cloud, but frankly it doesn't work as advertised and I still end up doing them manually. Vive le pen tool!