Tim Mallaileu, Program Manager on the Entity Framework team caused a big stir when he wrote the post Update on LINQ to SQL and LINQ to Entities Roadmap. It was such a big stir that he felt compelled to write a follow up post to clarify it: Clarifying the message on L2S Futures.
The essential message is that the Data Programmability team is de-emphasizing LINQ to SQL in favor of development of the Entity Framework product. It will still be available in Visual Studio for at least 10 years, but developers should not expect major improvements.
That leaves a conundrum for developers that have invested their precious time in mastering LINQ to SQL and have used it or are considering using it in production applications, including myself. Should we continue to use LINQ to SQL? I believe the answer is Yes!. The simple truth is that the Entity Framework is a v1 product and still has many shortcomings. I have nothing against the Entity Framework, I'm co-authoring a book on it.
The productivity boost available today from LINQ to SQL cannot be matched by Entity Framework. If you are starting development of a long-term strategic line-of-business application, then by all means adopt Entity Framework as your data-access strategy. For most everyday business applications where the objective is to quickly deliver the desired functionality and then move onto the next burning fire, LINQ to SQL provides a quick and effective data access mechanism that significantly shortens the development cycle. Use LINQ to SQL and enjoy it. I'm sure your clients will forgive you for your transgression as they enjoy their new software ahead of schedule and under budget.
In summary, the vast majority of business applications are a great use case for LINQ to SQL and will continue to be until Entity Framework is a rev or two further down the road.
Hope that helps.