There is a recently published whitepaper that talks about Microsoft AdCenter using SSAS 2008 to accelerate performance over 2005. Most of the paper is focused on upgrading and why you should do it. If you’re on 2005, the list is quite long but this will help you justify it if you’re struggling with that internally this should help you quantify some reasons.

http://technet.microsoft.com/en-us/library/ee410017.aspx