C# generics - what is gained by making a wrapper class generic?

Question

Consider this generic class:

public class Request<TOperation> 
    where TOperation : IOperation
{
    private TOperation _operation { get; set; }

    public string Method { get { return _operation.Method; } }

    public Request(TOperation operation)
    {
        _operation = operation;
    }
}

What real benefits does the generic version above offer over this non-generic version below?

public class Request
{
    private IOperation _operation { get; set; }

    public string Method { get { return _operation.Method; } }

    public Request(IOperation operation)
    {
        _operation = operation;
    }
}

The IOperation interface is:

public interface IOperation
{
    string Method { get; }
}

Answer 1

With the generic version a method could take a parameter of type Request<FooOperation>. Passing in an instance of Request<BarOperation> would be invalid.
So, the generic version enables methods to ensure they get a request for the correct operation.

Answer 2

In addition to all the other good answers, I'll add that the generic version does not take the boxing penalty if you happen to construct Request<T> with a T that is a value type that implements IOperation. The non-generic version boxes every time.