Chris, Paul,
Can you explain how you have pre-existing content as part of your subscription? When you create a trial, you have to create a new account. Did you then invite your existing user into the account? Or perhaps you were part of the beta program?
Currently there is no way to revert from a subscription back to a personal account. When you joined the organization, we display a strong warning message indicating this, something to the effect that all your content will be transferred to the organization and will no longer be accessible as an individual. Having said that, we are investigating what it would take to decouple a personal account from a subscription. There are a lot of different relationships that can get set up within an organization, like access to the organization's items and groups, so getting a clean break will be challenging to cover all the possibilities. Maybe in the case of Trial subscriptions, it might be easier...
Thanks,
Mike