While the reason Google Analytics failed at this has already been explained, GA Ecommerce tracking is near real-time, but not error corrected. Data in other parts can take several hours to show up, Google says to wait 24 hours for data to be complete and error corrected.
Omniture SiteCatalyst is near-real time. I don't know if they do some error correction later like GA does for Ecommerce data.
Conversion rates give you 'value': - 500 visits from source A, 10 sign ups, 2% conversion rate - 100 visits from source B, 10 sign ups, 10% conversion rate