Cover Flow is a nice looking interface, but it is eye candy far from a practical and useful interface. The biggest problem with Cover Flow is that the user can only view the currently selected album, the one before, and the one after (and only a fraction of the latter two). The reason why this is not useful has to do with the way we mentally process ordered lists.
Typically we view lists in words made up by letters- since the alphabet is standard and consistent, we are used to making sense of where a “G” falls in reference to the rest of the items in the list. It is an automatic mental process developed by our mastery of the alphabet and language. By contrast, Cover Flow forces us to constantly relearn our mental processes of ordering visual cues in the form of album covers. While you could argue that it is possible to learn the order of album art covers, it would take time and would be difficult since the list is dynamic.
We are all obsessed with album art and love visual interfaces, but a different approach needs to be taken in order to circumvent our natural understanding of language and ordered lists.