Performance is one of the crucial parts of any development project. If a user has to wait too long in an application, they will be dissatisfied and not keen on using the application. This is especially important for reporting applications. Many users can manage their daily job without reports; as an example, a sales representative can meet customers without having information about what the customer has bought previously, but the meeting will be more productive if they have this information. As a developer it is your responsibility to build a solution that performs. But what is good performance? If you ask a user, waiting more than 30 seconds is many times unacceptable for a report. If you have to wait that long, then it is very hard to do the ad-hoc analysis in an efficient way.
One of the main benefits of Analysis Services and other OLAP engines is the performance that you will get from them. The reason that you will get good...