Hmm. That's strange I got my Account Approval Notification on the same day as the payment receipt.
The account approval notification contains a link to the Getting Started area of the knowledge base, tells you your ftp username and password, tells you the name servers to use (if you're transferring a domain, which I was), tells you your web panel username and password, etc. It should be all you need.
Another possibility is that they just have too many signups to process right now due to the recent changes they made to their hosting plans (when I signed up it wasn't unlimited domains and 4800mb storage and all that)