I am using Entity Framework at my work and faced some problems.
Usually I hear about creating tiny Edmx´s files containing tables related to some Domain ie.: Help Desk Edmx, HR Edmx, etc. Instead of load all tables in one big Edmx, what would be much simpler, but for performance considerations(at design and build time mainly), it isn´t feasible.
It took me to some troubles, first about the commom tables, ie.: Employees Tables, it is at all Edmx´s, conflicting when I use a Employee class reference and have a using to both namespaces, then I have to reference the Empoyee class by the full name MyCompany.HelpDesk.Employee.
It doesn´t look natural.
I find myself repeatedly adding the same tables at all EDMX´s, it´s a rework, and I spend some minutes adding a table to entity framework design since I have 2k tables at Add Table Dialog.
Maybe VS2012 could be a solution to load 2k Tables at the same Edmx file(since the designer could be splitted), but I don´t believe that, because it delay to compile too, not only to open the designer.
Another option could be the Code First, but it doesn´t have a decent tool to Reverse Engineer the database to classes, since it tries to load all the tables from database, tooking about 2 hours!