[geckoday]

You need to use the Smarty eval function in the template to evaluate Smarty variables. Try changing this in checkout.tpl:

<td>{$payment_methods[payment].payment_details|default:"&nbsp;"}</td>

To this:

{eval var=$payment_methods[payment].payment_details assign="paydtls"}
<td>{$paydtls|default:"&nbsp;"}</td>