I wish I could migrate my normal Gmail account (all received email to date, current labels and rules) to my Google Apps for your domain account.
It would be time consuming especially if you have a lot of email, but it is possible. Set up your current account in an IMAP client like Thunderbird, download all the messages to local folders, set up the Apps account, move messages into that account.
I did that, and abandoned it in favor of regular gmail. Gmail for domains did not have (at that time - I don't know the sitation now) all the features of regular gmail and it had a fixed space quota.