The problem I can see is that its not totally type safe as you still need to run the code to check that your entity is compatible with the underlying table at runtime. If I am wrong here please correct me. It appears fairly easy to make a mistake on the datatype (Int vs Long) and have it blow up in your face when you run it. Sure the re-factoring is simple but I don't want to wait till runtime to catch these issues.

I don't think that its not achievable either. I think that LINQtoSQL and EntityFramework are the best implementation of database access that exists today. Import the database/table select over it with 95% assurance that the query will work at runtime and with the correct types. I really wish something like this existed in the Java world as I would switch in a heartbeat.

For the record I code C# mostly in my day job, but every time I move over to PHP/Java/Scala I miss LINQ. I am working with Play! at the moment and while the DB access is the best I have come across in the Java world, its still not at the same standard. I am still getting issues with simple selects where I should be using a Long rather then an Int.