In the couple weeks between when Salesforce upgrades the first instances and when they have finished rolling the new version out to everyone, it is a struggle to get a new package out. Currently, our packaging org has been upgraded to Winter 13, but the orgs we have designated for QA are still sitting at Summer 12. So, the attempt at installation of a new package for testing in our QA org results in the following error:
The AppExchange Application or component you have selected is not yet available on your instance of salesforce.com. Please check back in a few days to retry the installation. Press the back button of your browser now and bookmark the AppExchange Directory page so that you can find it later.
Consequently, if we need to get an emergency release to a customer, they are out of luck if their org is still waiting for the new Salesforce release.
Is this something we just have to live with or is there a way to work around it?