Hi
I owe a .NET development company and for last few year we have used our own ORM, that was quite easy to use and well functioning.
But for now we are in the process of switching to new technologies eg. ASP.NET MVC and the Entity Framework with LINQ. Both of those provide rapid application development and still allows to maintain code details.
LINQ to SQL will not be developed anymore, MS is going to support Entity Framework only (which is more powerfull).