Are you planning to migrate from licensed (installed/download) versions of Atlassian products to OnDemand?  Here are some useful resources to help your migration go smoothly.

JIRA

1. Check that you have enabled FishEye application access.  You’ll need this in order to upload your JIRA dump file via WebDAV.
2. Use cadaver for uploading your JIRA dump via WebDAV.

Confluence

1. Every Confluence Space must be migrated individually: Global & Personal
2. Verify that all user groups are added to OnDemand

FishEye

Migrating from our own Subversion repository to FishEye was the most challenging; perhaps because the migration is from a non-Atlassian product.

1. Before exporting your Subversion repository, make sure that you have a top-level directory for every JIRA project. This is required for the import.  Note that the project name is case-sensitive and must match the project key.  Additionally, each project directory must contain three directories: branches, tags, and trunk.  For detailed instructions, see Importing Versioned Data into Subversion.
2. If you need to rename one of your Subversion top-level directories to match your OnDemand project key, check out the handy tool svn-dump-reloc.
3. After completing the import, grant access to the top-level directory.  Without performing this step, we were unable to create or delete branches.  See Configuring repository permissions for a project.
4. OnDemand does not allow hooks on the repository.  If you are post-commit hooks on your existing repository, you’ll need to workaround the issue by creating a Subversion mirror and executing the hooks from this mirror.  See the instructions for this workaround in this comment.

If you want to learn more, come check out my talk at the 2012 Atlassian Summit in San Francisco.

Thanks to Allan Carhart and Jan-Michael Ong for doing all the heavy lifting during the migration!

Update: a video of my presentation is now live.