Don Smith is hinting at a new data access guidance package and is hoping for some feedback on the challenges you have in enterprise applications when incorporating the various Microsoft Data Access Technologies: LINQ To SQL, ADO.NET Entity Framework, etc.
Typically in enterprise applications you want to alleviate the coupling of your domain model on 3rd party dependencies - especially infrastructure related dependencies ( e.g. logging, data access, validation, etc. ). In particular, I find that the Microsoft Data Access Technologies are not developed to help you with this loose coupling and you end up spending a lot of time creating a generic wrapper around LINQ To SQL and Entity Framework which 1) can become a lot to maintain and 2) dilutes the usefulness sometimes. I am speaking from experience on doing this with LINQ To SQL :)
If you are interested in a new guidance package from Microsoft Patterns & Practices that may help you in the loose-coupling of Microsoft Data Access Technologies in your enterprise applications, I highly recommend you give Don Smith some feedback on his blog.
Data Access Tutorials