If anyone else is using eWay and the Gold Cart Plugin, this plugin is brilliant.
I've used WPEcommerce on a number of sites and two with eWay. I know from experience over the years when Instinct update WpEcommerce and the Gold Cart plugin itself, the eway.php file has been riddled with problems requiring numerous hacks and does not keep up.
At the time of writing, the latest WPEcommerce update rendered the admin and purchase receipt mail function for eWay transactions useless.
This is when I discovered this plugin which fixes everything. See http://www.buyfencing.com.au for example. Trust me, it is worth a swapping a small PayPal donation for the hours you will save!