A default SWD task will always report "complete" because it cannot accurately determine if something is installed properly or not. "Complete" just means that it ran all the lines of actionscript; it doesn't evaluate if the task remains relevant at the end. It's up to the user to modify the task (relevance, actionscript, action success criteria) in order to achieve exactly what they want.
Additionally, there are SWD logs that you can check to see if it reveals anything:
<BES Client folder>/__BESData/__Global/SWDDeployData