The skydome provides the ambient lighting which fills shadowed area as realistic natural lighting does.  However, the problem with this type of lighting is you lose diffuse and specular effects, the renders come out rather bland.  Most individuals will recommend a self lit skydome (Bagginsbill has the perfect one called an envsphere and it is free), and one infinite light at approximately 70% to similate a sunny day.  Run your render using IDL to simulate natural reflectiveness between surfaces. 

The only other factor present in the Pro series is gamma correction; this will actually enable you to use less light sets at a lower intensity to get a well balanced scene.  Considering that many light sets can and will increase your render time, this becomes a resource savings at best.

The link below is an example of what I described above.  There is a nudity warning, be adviced.

http://www.renderosity.com/mod/gallery/index.php?image_id=2152637&user_id=343328&np&np