The problem using GWO, and other methods that depend on the buyer viewing a post-checkout page where conversion-tracking code would be triggered, is that most checkouts with our system take place on a third-party site (e.g., paypal.com), where we have little-to-no control over the transition from the end of checkout there back to any post-checkout page. See "Notes on Conversion Tracking" here:
Also consider the article here for a more detailed understanding:
If you are selling downloads, then the buyer does need to visit your E-junkie thank-you page in order to claim their download, so you could just add the GWO conversion tracking code to your E-junkie thank-you page customization field(s):
If you are not selling downloads, I don't know if GWO can be made to work with Google E-commerce Tracking, but if it can, you could make Google Checkout your sole payment method, which would automatically be able to transmit all checkout data to Google E-commerce Tracking, so all your conversion tracking would be done from Google's end without relying on the buyer proceeding to a conversion page after checkout. You could combine that with Authorize.Net for a card-based direct-payment method, and in that case we can auto-redirect the buyer to your thank-you page after checkout. Checkouts involving PayPal, however, leave the problem where buyers who pay on PayPal's site cannot be auto-redirected to a thank-you page, so unless you're selling downloads (which give the buyer a need to visit that page at some point), conversion tracking with PayPal checkouts would be inherently inconsistent.