Hi Dave - I wouldn't worry that you are using CS4 (I steadfastly stuck to CS3 for years!!) - I have said it before but a dedicated user of earlier versions will invariably be more productive than a lazy user of later versions.
Don't get me wrong there are undeniably some excellent improvements that have been made along the way (for me particularly with the selection tools) but most techniques that are of any worth can be achieved with very early versions of Photoshop.
Interested to hear the type of Photoshop user you are? A photo manipulator, a compositor, a digital artist or perhaps a combination of all 3!