As announced on the official Commerce Server team blog yesterday – see http://tinyurl.com/yljcfwf for details or just follow http://blogs.msdn.com/commerce/  – SharePoint 2010 support will be coming to Commerce Server 2009 this summer.

This is obviously a very hot topic – as I have seen a lot of folks trying to get this to work today on either CS2009 or R2 CTP builds. In the interest in saving everyone some frustration, I thought I’d elaborate on some of the key changes being made in Commerce Server with respect to SharePoint 2010.

For those who have tried it – and hit a wall – the biggest obstacle is that authentication has changed substantially between SharePoint 2007 and SharePoint 2010. SharePoint 2010 now uses claims-based authentication based upon Windows Identity Foundation (formerly known as Geneva).

Unfortunately, what this means is that the Forms-based Authentication mechanism in Commerce Server 2009 is pretty much completely broken. This is not really a DIY debug/repair, as the changes needed are quite deep. 

This is just one facet of the work ongoing – besides making sure that sites can be easily provisioned, pages render correctly, and that there are no performance regressions, etc. that will all be made available this summer in the new Template Pack for SharePoint 2010.

Hope this helps!