First off, the Falcon 9 v1.1, of which this is the 3rd launch, uses a reusable first stage. Whether that stage is used in an expendable launch profile or in a reusable launch profile it's still the same hardware, the only significant difference is whether or not it has landing gear bolted on (which apparently they'll try to do for the next ISS cargo resupply launch). That's pretty significant because it means that they get additional testing and validation of their reusable first stage in a full up flight profile even on expendable launches like this one. The more they launch with this stage the more experience and confidence they get and the easier it will be to transition to a reusable flight profile.
Secondly, this launch should complete the certification program that enables the Falcon 9 v1.1 to be able to compete in EELV launches from NASA and DoD. Currently only the Atlas 5 and Delta IV fill that role (the original launchers developed out of the EELV program) and as a result United Launch Alliance (which operates both vehicles) get a significant amount of highly lucrative business. In 2014 there are 8 EELV launches, for example, and by around 2016 SpaceX could be launching EELV payloads. That's a tremendous amount of potential income for SpaceX (up to billions of dollars a year).
So, the SpaceX Manifest lists only two launches from Vandenberg in 2014 --- and one of them is the Falcon Heavy demo flight, for which no payload has yet been announced.
Manifest here: http://www.spacex.com/missions