It has some additional targets in there that the others don't have:
1. assert-ws-available: Check does the target server have the jbossws.sar deployed. Fail if it doesn't.
2. quickstart-specific-deploys: After deploying the .esb, this target is called. Quickstarts can override it to perform quickstart specific deployments.
Better again - get all the quickstarts to import the same base_build.xml from the root of the quickstarts