I would add that MDX allows you to create metrics for the cube users that take the information farther. You use it to create metrics such as percentages (eg completion percentage) that summarize the information in useful ways for your business users. That's a simple example. Averages are another common example. More advanced examples include rolling averages. If you are going to get good with SSAS, you will need to get good at MDX. Unfortunately I know of no good book that just addresses MDX within the context of SSAS, but I've seen good chapters in books. They can give you an idea of what is possible.