Architecture :: EF4 With Repository And Unit Of Work Patterns?

I've been reading recently about EF4, and how to build an architecture for asp.net web forms application using it.

I explored using POCOs (self tracking entities), with WCF, but found out that my application will be deployed on a single box (i.e. one tier), so I started reading about logical separation of layers, and came up with the following solution:

DAL layer that contains EDMX model and EF APIs, and also generated context object.Entities DLL that holds all generated POCO entities using ADO.NET POCO entity generator. (for persistence ignorance, and decoupling entities from DAL).Business layer that contains a façade for each related group of business functions, the façade will be aware of and using DAL layer. And in each function, it will initiate context and uses different entities to carry out specific job (i.e. function).UI layer that only calls the business layer façade classes. With no awareness of DAL, but it will be aware of entities (i.e. using entities DLL), as the business layer will return results basically as entity collections.

I want to know what you think about this architecture.

I also read about an architecture that uses repository and unit of work patterns, but what I understand that context object is already implementing a UOF pattern, and also object sets are implementing repository pattern (correct me if I'm wrong), so the only advantage of using additional abstraction over them is to make the business layer communicates to my classes, not EF classes, and this is good only if the DAL strategy might change (i.e. by using another tool other than EF, which is not my plan).