We are currently doing ecommerce package selection for a medium sized business with fairly advanced requirements (different pricing depending on customer group, ability to extend to support multiple languages and currencies, easy inventory updates through imports/exports etc). They are also after a site with a richly featured content management side to it (which I know SilverStripe would be ideal for).
In the absence of a features list - my rapid assessment of SilverStripe in the e-commerce area is that it is aiming to cover basic e-commerce requirements - rather than conquer the world of e-commerce - I assume that's fair?
Assuming my assessment is correct, is anyone aware of any cases where Silverstripe has been used together with osCommerce (I'm particularly interested in the typical pain areas - single sign-on - search integration etc)?
That is a fair assessment - the SilverStripe e-commerce module is basic, however like the rest of the SilverStripe CMS, it is very easy to extend and customise.
While I haven't looked at the code behind oscommerce, from what i gather from discussions with a guy who has looked at both the SilverStripe CMS code, and oscommerce, the SilverStripe code is much, much 'cleaner'. Apparently oscommerce has been written by ten different developers, each with quite different styles and skill sets, and as such is very hard to work with if you want to make it do anything different to what is does out of the box.
On the up side, oscommerce has been released, and will have a larger developer community around it.
We have made our final package selection and gone for X-Cart (also PHP based) rather than osCommerce (or Zen/CRE - its commercial cousins) - although CRE was a strong contender (benefits of open source married with modules which are well tested and commercially supported). One of the factors is exactly the one you highlighted - it's a bit of a dog's breakfast of coding styles. A good indication of this is the patch/upgrade procedures which tend to be a rather interesting combination of good luck and skilful analysis of file differences.
Although we believe we can cover the initial content management requirements by extending X-Cart - we are hoping that the the next phase of the project will give us another chance to play with SilverStripe.