In the realm of organic traffic, people tend to focus pretty exclusively on Google.com, and we as Web analysts are no exception. In doing this, we sometimes remain unaware of important metrics for organic traffic from other search engines.
It is very worthwhile to track goal completions and ecommerce activity for nonpaid, nonbranded traffic from each of the major search engines in your locale. There are inherent demographic and psychograpic differences in the user base for each search engine, so visitors from the various search engines may respond to your site quite differently.
If visitors from Bing are generating the highest conversion rate, you can perhaps focus a bit more of your search engine optimization efforts in that direction. If Google.co.uk visitors are generating the highest per-order ecommerce value, you could consider targeting more of your AdWords budget towards the UK.
Even more generally, remember to avoid the default organic advanced segment, since it includes branded traffic, and to break out country-specific search engines, particularly if your organization is located outside of the United States.