Have to say that that I think there was a point when Apple could have made a dent in at least the SMB enterprise market. They should have pushed Mac OS X Server and the XServes as a all in one business in a box solution like the old MS SBS product which Microsoft was breaking up when they thought they could make more money by selling separate products.
The "proper" OS X Server around Tiger, Leopard and Snow Leopard and the G5 and Intel Xserves made it a really good solution IMHO.
But then along came the iPhone and Apple Computer became Apple Inc, OS X Server became just an "app" and the Intel Xserves were killed off and they started offering Mac Minis as "servers". They just lost interest.