This is a limitation and one of the problems if using IPN. Since the IPN post back occurs sometime after the order is processed and the response is sent back to your IPN page it is not possible to display the status of the transaction at the time. You will only now the status of the transaction when it is posted to your IPN page.
What I normally suggest for IPN checkouts is that you update the db on the IPN page and also send an email to your user that let's them know if their transaction was successful like a receipt. The user could then come back to the site and login to see the details of their order or download goods or whatever else you would like to do.
The limitation is just the timing of this, you cannot ensure that the status of the transaction until after the IPN posts, and this will not happen before you redirect the user to the checkout success page.
