On the ADO.Net front:
AFAIK there were no major changes in ADO.Net for 3.5. System.Data.Linq aka LinqToSql is 100% tied to SqlServer. While we could probably re-implement a similar api, it would probably come without designer support which is less than desierable. The ADO.Net Entity Framework, which will give us all that LinqToSql is and more, is still scheduled for vnext at this point and I havent seen an estimated release date for vnext.