I have spoken to quite a few customers about LINQ & LINQ to SQL over the last few months.  Oddly enough, very few people have asked me about how one might encapsulate validation and business logic using LINQ to SQL.  Scott Guthrie just posted another in his LINQ to SQL series blogs here.  Part of his post covers some of the new features coming in beta 2 that make encapsulating your own validation and business logic using a new feature called partial methods.  Wes Dyer talks about partial methods here and here.  I was not aware of partial methods.  Pretty cool stuff.  The new validation hooks in LINQ to SQL definitely change the answer I give when people ask:).

-Marc